diff --git a/scripts/langindex.json b/scripts/langindex.json
index 9d82296e5..6f9b71abf 100644
--- a/scripts/langindex.json
+++ b/scripts/langindex.json
@@ -140,6 +140,7 @@
   "addon.calendar.sunday": "calendar",
   "addon.calendar.thu": "calendar",
   "addon.calendar.thursday": "calendar",
+  "addon.calendar.timebefore": "local_moodlemobileapp",
   "addon.calendar.today": "calendar",
   "addon.calendar.tomorrow": "calendar",
   "addon.calendar.tue": "calendar",
@@ -153,6 +154,7 @@
   "addon.calendar.typeopen": "calendar",
   "addon.calendar.typesite": "calendar",
   "addon.calendar.typeuser": "calendar",
+  "addon.calendar.units": "qtype_numerical",
   "addon.calendar.upcomingevents": "calendar",
   "addon.calendar.userevents": "calendar",
   "addon.calendar.wed": "calendar",
@@ -1562,6 +1564,7 @@
   "core.courses.therearecourses": "moodle",
   "core.courses.totalcoursesearchresults": "local_moodlemobileapp",
   "core.currentdevice": "local_moodlemobileapp",
+  "core.custom": "form",
   "core.datastoredoffline": "local_moodlemobileapp",
   "core.date": "moodle",
   "core.day": "moodle",
@@ -1944,6 +1947,8 @@
   "core.maxsizeandattachments": "moodle",
   "core.min": "moodle",
   "core.mins": "moodle",
+  "core.minute": "moodle",
+  "core.minutes": "moodle",
   "core.misc": "admin",
   "core.mod_assign": "assign/pluginname",
   "core.mod_assignment": "assignment/pluginname",
@@ -2284,6 +2289,8 @@
   "core.viewprofile": "moodle",
   "core.warningofflinedatadeleted": "local_moodlemobileapp",
   "core.warnopeninbrowser": "local_moodlemobileapp",
+  "core.week": "moodle",
+  "core.weeks": "moodle",
   "core.whatisyourage": "moodle",
   "core.wheredoyoulive": "moodle",
   "core.whoissiteadmin": "local_moodlemobileapp",
diff --git a/src/addons/calendar/components/calendar/calendar.ts b/src/addons/calendar/components/calendar/calendar.ts
index 5575e917c..a4b2178bc 100644
--- a/src/addons/calendar/components/calendar/calendar.ts
+++ b/src/addons/calendar/components/calendar/calendar.ts
@@ -94,7 +94,7 @@ export class AddonCalendarCalendarComponent implements OnInit, DoCheck, OnDestro
             this.obsDefaultTimeChange = CoreEvents.on(AddonCalendarProvider.DEFAULT_NOTIFICATION_TIME_CHANGED, () => {
                 this.weeks.forEach((week) => {
                     week.days.forEach((day) => {
-                        AddonCalendar.scheduleEventsNotifications(day.eventsFormated!);
+                        AddonCalendar.scheduleEventsNotifications(day.eventsFormated || []);
                     });
                 });
             }, this.currentSiteId);
@@ -150,7 +150,7 @@ export class AddonCalendarCalendarComponent implements OnInit, DoCheck, OnDestro
 
         if (this.weeks) {
             // Check if there's any change in the filter object.
-            const changes = this.differ.diff(this.filter!);
+            const changes = this.differ.diff(this.filter || {});
             if (changes) {
                 this.filterEvents();
             }
@@ -173,8 +173,8 @@ export class AddonCalendarCalendarComponent implements OnInit, DoCheck, OnDestro
             this.offlineEvents = AddonCalendarHelper.classifyIntoMonths(events);
 
             // Get the IDs of events edited in offline.
-            const filtered = events.filter((event) => event.id! > 0);
-            this.offlineEditedEventsIds = filtered.map((event) => event.id!);
+            const filtered = events.filter((event) => event.id > 0);
+            this.offlineEditedEventsIds = filtered.map((event) => event.id);
 
             return;
         }));
@@ -261,7 +261,7 @@ export class AddonCalendarCalendarComponent implements OnInit, DoCheck, OnDestro
                     isPast = day.ispast;
 
                     if (day.istoday) {
-                        day.eventsFormated!.forEach((event) => {
+                        day.eventsFormated?.forEach((event) => {
                             event.ispast = this.isEventPast(event);
                         });
                     }
@@ -306,8 +306,8 @@ export class AddonCalendarCalendarComponent implements OnInit, DoCheck, OnDestro
         this.weeks.forEach((week) => {
             week.days.forEach((day) => {
                 day.filteredEvents = AddonCalendarHelper.getFilteredEvents(
-                    day.eventsFormated!,
-                    this.filter!,
+                    day.eventsFormated || [],
+                    this.filter,
                     this.categories,
                 );
 
@@ -466,14 +466,14 @@ export class AddonCalendarCalendarComponent implements OnInit, DoCheck, OnDestro
             week.days.forEach((day) => {
 
                 // Schedule notifications for the events retrieved (only future events will be scheduled).
-                AddonCalendar.scheduleEventsNotifications(day.eventsFormated!);
+                AddonCalendar.scheduleEventsNotifications(day.eventsFormated || []);
 
                 if (monthOfflineEvents || this.deletedEvents.length) {
                     // There is offline data, merge it.
 
                     if (this.deletedEvents.length) {
                         // Mark as deleted the events that were deleted in offline.
-                        day.eventsFormated!.forEach((event) => {
+                        day.eventsFormated?.forEach((event) => {
                             event.deleted = this.deletedEvents.indexOf(event.id) != -1;
                         });
                     }
@@ -483,10 +483,10 @@ export class AddonCalendarCalendarComponent implements OnInit, DoCheck, OnDestro
                         day.events = day.events.filter((event) => this.offlineEditedEventsIds.indexOf(event.id) == -1);
                     }
 
-                    if (monthOfflineEvents && monthOfflineEvents[day.mday]) {
+                    if (monthOfflineEvents && monthOfflineEvents[day.mday] && day.eventsFormated) {
                         // Add the offline events (either new or edited).
                         day.eventsFormated =
-                            AddonCalendarHelper.sortEvents(day.eventsFormated!.concat(monthOfflineEvents[day.mday]));
+                            AddonCalendarHelper.sortEvents(day.eventsFormated.concat(monthOfflineEvents[day.mday]));
                     }
                 }
             });
@@ -505,7 +505,7 @@ export class AddonCalendarCalendarComponent implements OnInit, DoCheck, OnDestro
 
         this.weeks.forEach((week) => {
             week.days.forEach((day) => {
-                const event = day.eventsFormated!.find((event) => event.id == eventId);
+                const event = day.eventsFormated?.find((event) => event.id == eventId);
 
                 if (event) {
                     event.deleted = false;
@@ -521,7 +521,7 @@ export class AddonCalendarCalendarComponent implements OnInit, DoCheck, OnDestro
      * @return True if it's in the past.
      */
     protected isEventPast(event: { timestart: number; timeduration: number}): boolean {
-        return (event.timestart + event.timeduration) < this.currentTime!;
+        return (event.timestart + event.timeduration) < (this.currentTime || CoreTimeUtils.timestamp());
     }
 
     /**
diff --git a/src/addons/calendar/components/components.module.ts b/src/addons/calendar/components/components.module.ts
index 22b2b7100..283909027 100644
--- a/src/addons/calendar/components/components.module.ts
+++ b/src/addons/calendar/components/components.module.ts
@@ -19,12 +19,14 @@ import { CoreSharedModule } from '@/core/shared.module';
 import { AddonCalendarCalendarComponent } from './calendar/calendar';
 import { AddonCalendarUpcomingEventsComponent } from './upcoming-events/upcoming-events';
 import { AddonCalendarFilterPopoverComponent } from './filter/filter';
+import { AddonCalendarReminderTimeModalComponent } from './reminder-time-modal/reminder-time-modal';
 
 @NgModule({
     declarations: [
         AddonCalendarCalendarComponent,
         AddonCalendarUpcomingEventsComponent,
         AddonCalendarFilterPopoverComponent,
+        AddonCalendarReminderTimeModalComponent,
     ],
     imports: [
         CoreSharedModule,
@@ -35,6 +37,7 @@ import { AddonCalendarFilterPopoverComponent } from './filter/filter';
         AddonCalendarCalendarComponent,
         AddonCalendarUpcomingEventsComponent,
         AddonCalendarFilterPopoverComponent,
+        AddonCalendarReminderTimeModalComponent,
     ],
 })
 export class AddonCalendarComponentsModule {}
diff --git a/src/addons/calendar/components/reminder-time-modal/reminder-time-modal.html b/src/addons/calendar/components/reminder-time-modal/reminder-time-modal.html
new file mode 100644
index 000000000..ad47dee3a
--- /dev/null
+++ b/src/addons/calendar/components/reminder-time-modal/reminder-time-modal.html
@@ -0,0 +1,59 @@
+<ion-header>
+    <ion-toolbar>
+        <h2>{{ 'addon.calendar.reminders' | translate }}</h2>
+        <ion-buttons slot="end">
+            <ion-button fill="clear" (click)="closeModal()" [attr.aria-label]="'core.close' | translate">
+                <ion-icon slot="icon-only" name="fas-times" aria-hidden="true"></ion-icon>
+            </ion-button>
+        </ion-buttons>
+    </ion-toolbar>
+</ion-header>
+<ion-content>
+    <ion-radio-group [(ngModel)]="radioValue" class="ion-text-wrap">
+        <!-- Preset options. -->
+        <ion-item *ngIf="allowDisable">
+            <ion-label>
+                <p>{{ 'core.settings.disabled' | translate }}</p>
+            </ion-label>
+            <ion-radio slot="end" value="disabled"></ion-radio>
+        </ion-item>
+        <ion-item *ngFor="let option of presetOptions">
+            <ion-label>
+                <p>{{ option.label }}</p>
+            </ion-label>
+            <ion-radio slot="end" [value]="option.radioValue"></ion-radio>
+        </ion-item>
+
+        <!-- Custom value. -->
+        <ion-item lines="none" class="ion-text-wrap">
+            <ion-label>
+                <p>{{ 'core.custom' | translate }}</p>
+            </ion-label>
+            <ion-radio slot="end" value="custom"></ion-radio>
+        </ion-item>
+        <ion-item class="ion-text-wrap">
+            <ion-label></ion-label>
+
+            <div class="flex-row">
+                <!-- Input to enter the value. -->
+                <ion-input type="number" name="customvalue" [(ngModel)]="customValue" [disabled]="radioValue != 'custom'"
+                    placeholder="10">
+                </ion-input>
+
+                <!-- Units. -->
+                <label class="accesshide" for="reminderUnits">{{ 'addon.calendar.units' | translate }}</label>
+                <ion-select id="reminderUnits" name="customunits" [(ngModel)]="customUnits" interface="action-sheet"
+                    [disabled]="radioValue != 'custom'" slot="end"
+                    [interfaceOptions]="{header: 'addon.calendar.units' | translate}">
+                    <ion-select-option *ngFor="let option of customUnitsOptions" [value]="option.value">
+                        {{ option.label | translate }}
+                    </ion-select-option>
+                </ion-select>
+            </div>
+        </ion-item>
+    </ion-radio-group>
+
+    <ion-button class="ion-margin" expand="block" (click)="saveReminder()" [disabled]="radioValue == 'custom' && !customValue">
+        {{ 'core.done' | translate }}
+    </ion-button>
+</ion-content>
diff --git a/src/addons/calendar/components/reminder-time-modal/reminder-time-modal.ts b/src/addons/calendar/components/reminder-time-modal/reminder-time-modal.ts
new file mode 100644
index 000000000..f505fde21
--- /dev/null
+++ b/src/addons/calendar/components/reminder-time-modal/reminder-time-modal.ts
@@ -0,0 +1,156 @@
+// (C) Copyright 2015 Moodle Pty Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import { AddonCalendar, AddonCalendarReminderUnits, AddonCalendarValueAndUnit } from '@addons/calendar/services/calendar';
+import { Component, Input, OnInit } from '@angular/core';
+import { CoreDomUtils } from '@services/utils/dom';
+import { ModalController } from '@singletons';
+
+/**
+ * Modal to choose a reminder time.
+ */
+@Component({
+    selector: 'addon-calendar-new-reminder-modal',
+    templateUrl: 'reminder-time-modal.html',
+})
+export class AddonCalendarReminderTimeModalComponent implements OnInit {
+
+    @Input() initialValue?: AddonCalendarValueAndUnit;
+    @Input() allowDisable?: boolean;
+
+    radioValue = '5m';
+    customValue = '10';
+    customUnits = AddonCalendarReminderUnits.MINUTE;
+
+    presetOptions = [
+        {
+            radioValue: '5m',
+            value: 5,
+            unit: AddonCalendarReminderUnits.MINUTE,
+            label: '',
+        },
+        {
+            radioValue: '10m',
+            value: 10,
+            unit: AddonCalendarReminderUnits.MINUTE,
+            label: '',
+        },
+        {
+            radioValue: '30m',
+            value: 30,
+            unit: AddonCalendarReminderUnits.MINUTE,
+            label: '',
+        },
+        {
+            radioValue: '1h',
+            value: 1,
+            unit: AddonCalendarReminderUnits.HOUR,
+            label: '',
+        },
+        {
+            radioValue: '12h',
+            value: 12,
+            unit: AddonCalendarReminderUnits.HOUR,
+            label: '',
+        },
+        {
+            radioValue: '1d',
+            value: 1,
+            unit: AddonCalendarReminderUnits.DAY,
+            label: '',
+        },
+    ];
+
+    customUnitsOptions = [
+        {
+            value: AddonCalendarReminderUnits.MINUTE,
+            label: 'core.minutes',
+        },
+        {
+            value: AddonCalendarReminderUnits.HOUR,
+            label: 'core.hours',
+        },
+        {
+            value: AddonCalendarReminderUnits.DAY,
+            label: 'core.days',
+        },
+        {
+            value: AddonCalendarReminderUnits.WEEK,
+            label: 'core.weeks',
+        },
+    ];
+
+    /**
+     * @inheritdoc
+     */
+    async ngOnInit(): Promise<void> {
+        this.presetOptions.forEach((option) => {
+            option.label = AddonCalendar.getUnitValueLabel(option.value, option.unit);
+        });
+
+        if (!this.initialValue) {
+            return;
+        }
+
+        if (this.initialValue.value === 0) {
+            this.radioValue = 'disabled';
+        } else {
+            // Search if it's one of the preset options.
+            const option = this.presetOptions.find(option =>
+                option.value === this.initialValue?.value && option.unit === this.initialValue.unit);
+
+            if (option) {
+                this.radioValue = option.radioValue;
+            } else {
+                // It's a custom value.
+                this.radioValue = 'custom';
+                this.customValue = String(this.initialValue.value);
+                this.customUnits = this.initialValue.unit;
+            }
+        }
+    }
+
+    /**
+     * Close the modal.
+     */
+    closeModal(): void {
+        ModalController.dismiss();
+    }
+
+    /**
+     * Save the reminder.
+     */
+    saveReminder(): void {
+        if (this.radioValue === 'disabled') {
+            ModalController.dismiss(0);
+        } else if (this.radioValue === 'custom') {
+            const value = parseInt(this.customValue, 10);
+            if (!value) {
+                CoreDomUtils.showErrorModal('core.errorinvalidform', true);
+
+                return;
+            }
+
+            ModalController.dismiss(Math.abs(value) * this.customUnits);
+        } else {
+            const option = this.presetOptions.find(option => option.radioValue === this.radioValue);
+            if (!option) {
+                return;
+            }
+
+            ModalController.dismiss(option.unit * option.value);
+        }
+    }
+
+}
diff --git a/src/addons/calendar/components/upcoming-events/upcoming-events.ts b/src/addons/calendar/components/upcoming-events/upcoming-events.ts
index 7566c6d14..f59363845 100644
--- a/src/addons/calendar/components/upcoming-events/upcoming-events.ts
+++ b/src/addons/calendar/components/upcoming-events/upcoming-events.ts
@@ -106,7 +106,7 @@ export class AddonCalendarUpcomingEventsComponent implements OnInit, DoCheck, On
      */
     ngDoCheck(): void {
         // Check if there's any change in the filter object.
-        const changes = this.differ.diff(this.filter!);
+        const changes = this.differ.diff(this.filter || {});
         if (changes) {
             this.filterEvents();
         }
@@ -183,7 +183,7 @@ export class AddonCalendarUpcomingEventsComponent implements OnInit, DoCheck, On
 
         // Re-calculate the formatted time so it uses the device date.
         const promises = this.events.map((event) =>
-            AddonCalendar.formatEventTime(event, this.timeFormat!).then((time) => {
+            AddonCalendar.formatEventTime(event, this.timeFormat).then((time) => {
                 event.formattedtime = time;
 
                 return;
@@ -221,7 +221,7 @@ export class AddonCalendarUpcomingEventsComponent implements OnInit, DoCheck, On
      * Filter events based on the filter popover.
      */
     protected filterEvents(): void {
-        this.filteredEvents = AddonCalendarHelper.getFilteredEvents(this.events, this.filter!, this.categories);
+        this.filteredEvents = AddonCalendarHelper.getFilteredEvents(this.events, this.filter, this.categories);
     }
 
     /**
diff --git a/src/addons/calendar/lang.json b/src/addons/calendar/lang.json
index 8b1748f6b..a71e8921b 100644
--- a/src/addons/calendar/lang.json
+++ b/src/addons/calendar/lang.json
@@ -41,6 +41,7 @@
     "noevents": "There are no events",
     "nopermissiontoupdatecalendar": "Sorry, but you do not have permission to update the calendar event.",
     "reminders": "Reminders",
+    "units": "Units",
     "repeatedevents": "Repeated events",
     "repeateditall": "Also apply changes to the other {{$a}} events in this repeat series",
     "repeateditthis": "Apply changes to this event only",
@@ -54,6 +55,7 @@
     "sunday": "Sunday",
     "thu": "Thu",
     "thursday": "Thursday",
+    "timebefore": "{{value}} {{units}} before",
     "today": "Today",
     "tomorrow": "Tomorrow",
     "tue": "Tue",
@@ -73,4 +75,4 @@
     "wednesday": "Wednesday",
     "when": "When",
     "yesterday": "Yesterday"
-}
\ No newline at end of file
+}
diff --git a/src/addons/calendar/pages/day/day.page.ts b/src/addons/calendar/pages/day/day.page.ts
index f02bc54d1..19963cb62 100644
--- a/src/addons/calendar/pages/day/day.page.ts
+++ b/src/addons/calendar/pages/day/day.page.ts
@@ -286,7 +286,7 @@ export class AddonCalendarDayPage implements OnInit, OnDestroy {
                 this.offlineEvents = AddonCalendarHelper.classifyIntoMonths(offlineEvents);
 
                 // Get the IDs of events edited in offline.
-                this.offlineEditedEventsIds = offlineEvents.filter((event) => event.id! > 0).map((event) => event.id!);
+                this.offlineEditedEventsIds = offlineEvents.filter((event) => event.id > 0).map((event) => event.id);
 
                 return;
             }));
@@ -361,7 +361,7 @@ export class AddonCalendarDayPage implements OnInit, OnDestroy {
         const promises = this.events.map((event) => {
             event.ispast = this.isPastDay || (this.isCurrentDay && this.isEventPast(event));
 
-            return AddonCalendar.formatEventTime(event, this.timeFormat!, true, dayTime).then((time) => {
+            return AddonCalendar.formatEventTime(event, this.timeFormat, true, dayTime).then((time) => {
                 event.formattedtime = time;
 
                 return;
@@ -521,12 +521,7 @@ export class AddonCalendarDayPage implements OnInit, OnDestroy {
      * @param eventId Event to load.
      */
     gotoEvent(eventId: number): void {
-        if (eventId < 0) {
-            // It's an offline event, go to the edit page.
-            this.openEdit(eventId);
-        } else {
-            CoreNavigator.navigateToSitePath(`/calendar/event/${eventId}`);
-        }
+        CoreNavigator.navigateToSitePath(`/calendar/event/${eventId}`);
     }
 
     /**
diff --git a/src/addons/calendar/pages/edit-event/edit-event.html b/src/addons/calendar/pages/edit-event/edit-event.html
index 859291287..469fc2e7c 100644
--- a/src/addons/calendar/pages/edit-event/edit-event.html
+++ b/src/addons/calendar/pages/edit-event/edit-event.html
@@ -113,120 +113,129 @@
                 </ion-item>
             </ng-container>
 
-            <!-- Advanced options. -->
-            <ion-item button class="ion-text-wrap divider" (click)="toggleAdvanced()" detail="false">
-                <ion-icon *ngIf="!advanced" name="fas-caret-right" flip-rtl slot="start" aria-hidden="true"></ion-icon>
-                <ion-icon *ngIf="advanced" name="fas-caret-down" slot="start" aria-hidden="true"></ion-icon>
-                <ion-label>
-                    <p class="item-heading" *ngIf="!advanced">{{ 'core.showmore' | translate }}</p>
-                    <p class="item-heading" *ngIf="advanced">{{ 'core.showless' | translate }}</p>
-                </ion-label>
-            </ion-item>
-
-            <div [hidden]="!advanced">
-                <!-- Description. -->
-                <ion-item class="ion-text-wrap">
-                    <ion-label position="stacked">
-                        <p class="item-heading">{{ 'core.description' | translate }}</p>
+            <!-- Reminders. Right now, only allow adding them here for new events. -->
+            <ng-container *ngIf="notificationsEnabled && !eventId">
+                <ion-item-divider class="addon-calendar-reminders-title">
+                    <ion-label>
+                        <p class="item-heading">{{ 'addon.calendar.reminders' | translate }}</p>
                     </ion-label>
-                    <core-rich-text-editor [control]="descriptionControl" [attr.aria-label]="'core.description' | translate"
-                        [placeholder]="'core.description' | translate" name="description" [component]="component"
-                        [componentId]="eventId" [autoSave]="false"></core-rich-text-editor>
+                    <ion-button fill="clear" color="dark" (click)="addReminder()" slot="end"
+                        [attr.aria-label]="'addon.calendar.setnewreminder' | translate">
+                        <ion-icon name="fas-plus" slot="icon-only" aria-hidden="true"></ion-icon>
+                    </ion-button>
+                </ion-item-divider>
+                <ion-item *ngFor="let reminder of reminders" class="ion-text-wrap">
+                    <ion-label>
+                        <p>{{ reminder.label }}</p>
+                    </ion-label>
+                    <ion-button fill="clear" (click)="removeReminder(reminder)" [attr.aria-label]="'core.delete' | translate"
+                        slot="end">
+                        <ion-icon name="fas-trash" color="danger" slot="icon-only" aria-hidden="true"></ion-icon>
+                    </ion-button>
                 </ion-item>
+            </ng-container>
 
-                <!-- Location. -->
+            <!-- Duration. -->
+            <div class="ion-text-wrap addon-calendar-radio-container">
+                <ion-radio-group formControlName="duration">
+                    <ion-item-divider class="addon-calendar-radio-title">
+                        <ion-label>
+                            <p class="item-heading">{{ 'addon.calendar.eventduration' | translate }}</p>
+                        </ion-label>
+                    </ion-item-divider>
+                    <ion-item>
+                        <ion-label>
+                            <p>{{ 'addon.calendar.durationnone' | translate }}</p>
+                        </ion-label>
+                        <ion-radio slot="end" [value]="0"></ion-radio>
+                    </ion-item>
+                    <ion-item lines="none">
+                        <ion-label>
+                            <p>{{ 'addon.calendar.durationuntil' | translate }}</p>
+                        </ion-label>
+                        <ion-radio slot="end" [value]="1"></ion-radio>
+                    </ion-item>
+                    <ion-item *ngIf="form.controls.duration.value === 1">
+                        <ion-label position="stacked"></ion-label>
+                        <ion-datetime formControlName="timedurationuntil" [max]="maxDate" [min]="minDate"
+                            [placeholder]="'addon.calendar.durationuntil' | translate"
+                            [displayFormat]="dateFormat" display-timezone="utc">
+                        </ion-datetime>
+                    </ion-item>
+                    <ion-item lines="none">
+                        <ion-label>
+                            <p>{{ 'addon.calendar.durationminutes' | translate }}</p>
+                        </ion-label>
+                        <ion-radio slot="end" [value]="2"></ion-radio>
+                    </ion-item>
+                    <ion-item *ngIf="form.controls.duration.value === 2">
+                        <ion-label class="sr-only">{{ 'addon.calendar.durationminutes' | translate }}</ion-label>
+                        <ion-input type="number" name="timedurationminutes" slot="end"
+                            [placeholder]="'addon.calendar.durationminutes' | translate"
+                            formControlName="timedurationminutes"></ion-input>
+                    </ion-item>
+                </ion-radio-group>
+            </div>
+
+            <!-- Repeat (for new events). -->
+            <ng-container *ngIf="!eventId || eventId < 0">
+                <ion-item class="ion-text-wrap divider" lines="none">
+                    <ion-label>
+                        <p class="item-heading">{{ 'addon.calendar.repeatevent' | translate }}</p>
+                    </ion-label>
+                    <ion-checkbox slot="end" formControlName="repeat"></ion-checkbox>
+                </ion-item>
                 <ion-item class="ion-text-wrap">
                     <ion-label position="stacked">
-                        <p class="item-heading">{{ 'core.location' | translate }}</p>
+                        <p>{{ 'addon.calendar.repeatweeksl' | translate }}</p>
                     </ion-label>
-                    <ion-input type="text" name="location" [placeholder]="'core.location' | translate" formControlName="location">
+                    <ion-input type="number" name="repeats" formControlName="repeats" [disabled]="!form.controls.repeat.value">
                     </ion-input>
                 </ion-item>
+            </ng-container>
 
-                <!-- Duration. -->
-                <div class="ion-text-wrap addon-calendar-radio-container">
-                    <ion-radio-group formControlName="duration">
-                        <ion-item-divider class="addon-calendar-radio-title">
-                            <ion-label>
-                                <p class="item-heading">{{ 'addon.calendar.eventduration' | translate }}</p>
-                            </ion-label>
-                        </ion-item-divider>
-                        <ion-item>
-                            <ion-label>
-                                <p>{{ 'addon.calendar.durationnone' | translate }}</p>
-                            </ion-label>
-                            <ion-radio slot="end" [value]="0"></ion-radio>
-                        </ion-item>
-                        <ion-item lines="none">
-                            <ion-label>
-                                <p>{{ 'addon.calendar.durationuntil' | translate }}</p>
-                            </ion-label>
-                            <ion-radio slot="end" [value]="1"></ion-radio>
-                        </ion-item>
-                        <ion-item>
-                            <ion-label position="stacked"></ion-label>
-                            <ion-datetime formControlName="timedurationuntil" [max]="maxDate" [min]="minDate"
-                                [placeholder]="'addon.calendar.durationuntil' | translate"
-                                [displayFormat]="dateFormat" [disabled]="form.controls.duration.value != 1"
-                                display-timezone="utc">
-                            </ion-datetime>
-                        </ion-item>
-                        <ion-item lines="none">
-                            <ion-label>
-                                <p>{{ 'addon.calendar.durationminutes' | translate }}</p>
-                            </ion-label>
-                            <ion-radio slot="end" [value]="2"></ion-radio>
-                        </ion-item>
-                        <ion-item>
-                            <ion-label class="sr-only">{{ 'addon.calendar.durationminutes' | translate }}</ion-label>
-                            <ion-input type="number" name="timedurationminutes" slot="end"
-                                [placeholder]="'addon.calendar.durationminutes' | translate"
-                                formControlName="timedurationminutes" [disabled]="form.controls.duration.value != 2"></ion-input>
-                        </ion-item>
-                    </ion-radio-group>
-                </div>
-
-                <!-- Repeat (for new events). -->
-                <ng-container *ngIf="!eventId || eventId < 0">
-                    <ion-item class="ion-text-wrap divider" lines="none">
+            <!-- Apply to all events or just this one (editing repeated events). -->
+            <div *ngIf="eventRepeatId" class="ion-text-wrap addon-calendar-radio-container">
+                <ion-radio-group formControlName="repeateditall">
+                    <ion-item-divider class="addon-calendar-radio-title">
                         <ion-label>
-                            <p class="item-heading">{{ 'addon.calendar.repeatevent' | translate }}</p>
+                            <p class="item-heading">{{ 'addon.calendar.repeatedevents' | translate }}</p>
                         </ion-label>
-                        <ion-checkbox slot="end" formControlName="repeat"></ion-checkbox>
-                    </ion-item>
-                    <ion-item class="ion-text-wrap">
-                        <ion-label position="stacked">
-                            <p>{{ 'addon.calendar.repeatweeksl' | translate }}</p>
+                    </ion-item-divider>
+                    <ion-item>
+                        <ion-label>
+                            <p>{{ 'addon.calendar.repeateditall' | translate:{$a: otherEventsCount} }}</p>
                         </ion-label>
-                        <ion-input type="number" name="repeats" formControlName="repeats" [disabled]="!form.controls.repeat.value">
-                        </ion-input>
+                        <ion-radio slot="end" value="1"></ion-radio>
                     </ion-item>
-                </ng-container>
-
-                <!-- Apply to all events or just this one (editing repeated events). -->
-                <div *ngIf="eventRepeatId" class="ion-text-wrap addon-calendar-radio-container">
-                    <ion-radio-group formControlName="repeateditall">
-                        <ion-item-divider class="addon-calendar-radio-title">
-                            <ion-label>
-                                <p class="item-heading">{{ 'addon.calendar.repeatedevents' | translate }}</p>
-                            </ion-label>
-                        </ion-item-divider>
-                        <ion-item>
-                            <ion-label>
-                                <p>{{ 'addon.calendar.repeateditall' | translate:{$a: otherEventsCount} }}</p>
-                            </ion-label>
-                            <ion-radio slot="end" value="1"></ion-radio>
-                        </ion-item>
-                        <ion-item>
-                            <ion-label>
-                                <p>{{ 'addon.calendar.repeateditthis' | translate }}</p>
-                            </ion-label>
-                            <ion-radio slot="end" value="0"></ion-radio>
-                        </ion-item>
-                    </ion-radio-group>
-                </div>
+                    <ion-item>
+                        <ion-label>
+                            <p>{{ 'addon.calendar.repeateditthis' | translate }}</p>
+                        </ion-label>
+                        <ion-radio slot="end" value="0"></ion-radio>
+                    </ion-item>
+                </ion-radio-group>
             </div>
 
+            <!-- Description. -->
+            <ion-item class="ion-text-wrap">
+                <ion-label position="stacked">
+                    <p class="item-heading">{{ 'core.description' | translate }}</p>
+                </ion-label>
+                <core-rich-text-editor [control]="descriptionControl" [attr.aria-label]="'core.description' | translate"
+                    [placeholder]="'core.description' | translate" name="description" [component]="component"
+                    [componentId]="eventId" [autoSave]="false"></core-rich-text-editor>
+            </ion-item>
+
+            <!-- Location. -->
+            <ion-item class="ion-text-wrap">
+                <ion-label position="stacked">
+                    <p class="item-heading">{{ 'core.location' | translate }}</p>
+                </ion-label>
+                <ion-input type="text" name="location" [placeholder]="'core.location' | translate" formControlName="location">
+                </ion-input>
+            </ion-item>
+
             <ion-item>
                 <ion-label>
                     <ion-row>
diff --git a/src/addons/calendar/pages/edit-event/edit-event.page.ts b/src/addons/calendar/pages/edit-event/edit-event.page.ts
index 366e07fa9..d7bcfd094 100644
--- a/src/addons/calendar/pages/edit-event/edit-event.page.ts
+++ b/src/addons/calendar/pages/edit-event/edit-event.page.ts
@@ -33,7 +33,7 @@ import {
     AddonCalendarSubmitCreateUpdateFormDataWSParams,
 } from '../../services/calendar';
 import { AddonCalendarOffline } from '../../services/calendar-offline';
-import { AddonCalendarEventTypeOption, AddonCalendarHelper } from '../../services/calendar-helper';
+import { AddonCalendarEventReminder, AddonCalendarEventTypeOption, AddonCalendarHelper } from '../../services/calendar-helper';
 import { AddonCalendarSync, AddonCalendarSyncProvider } from '../../services/calendar-sync';
 import { CoreSite } from '@classes/site';
 import { Translate } from '@singletons';
@@ -43,6 +43,8 @@ import { CoreError } from '@classes/errors/error';
 import { CoreNavigator } from '@services/navigator';
 import { CanLeave } from '@guards/can-leave';
 import { CoreForms } from '@singletons/form';
+import { CoreLocalNotifications } from '@services/local-notifications';
+import { AddonCalendarReminderTimeModalComponent } from '@addons/calendar/components/reminder-time-modal/reminder-time-modal';
 
 /**
  * Page that displays a form to create/edit an event.
@@ -68,7 +70,6 @@ export class AddonCalendarEditEventPage implements OnInit, OnDestroy, CanLeave {
     groups: CoreGroup[] = [];
     loadingGroups = false;
     courseGroupSet = false;
-    advanced = false;
     errors: Record<string, string>;
     error = false;
     eventRepeatId?: number;
@@ -83,6 +84,10 @@ export class AddonCalendarEditEventPage implements OnInit, OnDestroy, CanLeave {
     groupControl: FormControl;
     descriptionControl: FormControl;
 
+    // Reminders.
+    notificationsEnabled = false;
+    reminders: AddonCalendarEventCandidateReminder[] = [];
+
     protected courseId!: number;
     protected originalData?: AddonCalendarOfflineEventDBRecord;
     protected currentSite: CoreSite;
@@ -95,6 +100,7 @@ export class AddonCalendarEditEventPage implements OnInit, OnDestroy, CanLeave {
         protected fb: FormBuilder,
     ) {
         this.currentSite = CoreSites.getRequiredCurrentSite();
+        this.notificationsEnabled = CoreLocalNotifications.isAvailable();
         this.errors = {
             required: Translate.instant('core.required'),
         };
@@ -140,6 +146,7 @@ export class AddonCalendarEditEventPage implements OnInit, OnDestroy, CanLeave {
         this.form.addControl('timedurationuntil', this.fb.control(currentDate));
         this.form.addControl('courseid', this.fb.control(this.courseId));
 
+        this.initReminders();
         this.fetchData().finally(() => {
             this.originalData = CoreUtils.clone(this.form.value);
             this.loaded = true;
@@ -171,17 +178,19 @@ export class AddonCalendarEditEventPage implements OnInit, OnDestroy, CanLeave {
 
             if (this.eventId && !this.gotEventData) {
                 // Editing an event, get the event data. Wait for sync first.
+                const eventId = this.eventId;
+
                 promises.push(AddonCalendarSync.waitForSync(AddonCalendarSyncProvider.SYNC_ID).then(async () => {
                     // Do not block if the scope is already destroyed.
                     if (!this.isDestroyed && this.eventId) {
-                        CoreSync.blockOperation(AddonCalendarProvider.COMPONENT, this.eventId);
+                        CoreSync.blockOperation(AddonCalendarProvider.COMPONENT, eventId);
                     }
 
                     let eventForm: AddonCalendarEvent | AddonCalendarOfflineEventDBRecord | undefined;
 
                     // Get the event offline data if there's any.
                     try {
-                        eventForm = await AddonCalendarOffline.getEvent(this.eventId!);
+                        eventForm = await AddonCalendarOffline.getEvent(eventId);
 
                         this.hasOffline = true;
                     } catch {
@@ -189,9 +198,9 @@ export class AddonCalendarEditEventPage implements OnInit, OnDestroy, CanLeave {
                         this.hasOffline = false;
                     }
 
-                    if (this.eventId! > 0) {
+                    if (eventId > 0) {
                         // It's an online event. get its data from server.
-                        const event = await AddonCalendar.getEventById(this.eventId!);
+                        const event = await AddonCalendar.getEventById(eventId);
 
                         if (!eventForm) {
                             eventForm = event; // Use offline data first.
@@ -431,13 +440,6 @@ export class AddonCalendarEditEventPage implements OnInit, OnDestroy, CanLeave {
         }
     }
 
-    /**
-     * Show or hide advanced form fields.
-     */
-    toggleAdvanced(): void {
-        this.advanced = !this.advanced;
-    }
-
     selectDuration(duration: string): void {
         this.form.controls.duration.setValue(duration);
     }
@@ -517,7 +519,9 @@ export class AddonCalendarEditEventPage implements OnInit, OnDestroy, CanLeave {
         let event: AddonCalendarEvent | AddonCalendarOfflineEventDBRecord;
 
         try {
-            const result = await AddonCalendar.submitEvent(this.eventId, data);
+            const result = await AddonCalendar.submitEvent(this.eventId, data, {
+                reminders: this.reminders,
+            });
             event = result.event;
 
             CoreForms.triggerFormSubmittedEvent(this.formElement, result.sent, this.currentSite.getId());
@@ -562,7 +566,10 @@ export class AddonCalendarEditEventPage implements OnInit, OnDestroy, CanLeave {
             if (event) {
                 CoreEvents.trigger(
                     AddonCalendarProvider.NEW_EVENT_EVENT,
-                    { eventId: event.id! },
+                    {
+                        eventId: event.id,
+                        oldEventId: this.eventId,
+                    },
                     this.currentSite.getId(),
                 );
             } else {
@@ -578,10 +585,15 @@ export class AddonCalendarEditEventPage implements OnInit, OnDestroy, CanLeave {
      * Discard an offline saved discussion.
      */
     async discard(): Promise<void> {
+        if (!this.eventId) {
+            return;
+        }
+
         try {
             await CoreDomUtils.showConfirm(Translate.instant('core.areyousure'));
+
             try {
-                await AddonCalendarOffline.deleteEvent(this.eventId!);
+                await AddonCalendarOffline.deleteEvent(this.eventId);
 
                 CoreForms.triggerFormCancelledEvent(this.formElement, this.currentSite.getId());
 
@@ -620,6 +632,69 @@ export class AddonCalendarEditEventPage implements OnInit, OnDestroy, CanLeave {
         }
     }
 
+    /**
+     * Init reminders.
+     *
+     * @return Promise resolved when done.
+     */
+    protected async initReminders(): Promise<void> {
+        if (!this.notificationsEnabled) {
+            return;
+        }
+
+        // Check if default reminders are enabled.
+        const defaultTime = await AddonCalendar.getDefaultNotificationTime(this.currentSite.getId());
+        if (defaultTime === 0) {
+            return;
+        }
+
+        const data = AddonCalendarProvider.convertSecondsToValueAndUnit(defaultTime);
+
+        // Add default reminder.
+        this.reminders.push({
+            time: null,
+            value: data.value,
+            unit: data.unit,
+            label: AddonCalendar.getUnitValueLabel(data.value, data.unit, true),
+        });
+    }
+
+    /**
+     * Add a reminder.
+     */
+    async addReminder(): Promise<void> {
+        const reminderTime = await CoreDomUtils.openModal<number>({
+            component: AddonCalendarReminderTimeModalComponent,
+        });
+
+        if (reminderTime === undefined) {
+            // User canceled.
+            return;
+        }
+
+        const data = AddonCalendarProvider.convertSecondsToValueAndUnit(reminderTime);
+
+        // Add reminder.
+        this.reminders.push({
+            time: reminderTime,
+            value: data.value,
+            unit: data.unit,
+            label: AddonCalendar.getUnitValueLabel(data.value, data.unit),
+        });
+    }
+
+    /**
+     * Remove a reminder.
+     *
+     * @param reminder The reminder to remove.
+     */
+    removeReminder(reminder: AddonCalendarEventCandidateReminder): void {
+        const index = this.reminders.indexOf(reminder);
+        if (index != -1) {
+            this.reminders.splice(index, 1);
+        }
+    }
+
     /**
      * Page destroyed.
      */
@@ -629,3 +704,5 @@ export class AddonCalendarEditEventPage implements OnInit, OnDestroy, CanLeave {
     }
 
 }
+
+type AddonCalendarEventCandidateReminder = Omit<AddonCalendarEventReminder, 'id'|'eventid'>;
diff --git a/src/addons/calendar/pages/event/event.html b/src/addons/calendar/pages/event/event.html
index 493b41712..e2279bd11 100644
--- a/src/addons/calendar/pages/event/event.html
+++ b/src/addons/calendar/pages/event/event.html
@@ -21,8 +21,8 @@
                     [priority]="400" [content]="'core.settings.synchronizenow' | translate" (action)="doRefresh(undefined, $event, true)"
                     [iconAction]="syncIcon" [closeOnClick]="false">
                 </core-context-menu-item>
-                <core-context-menu-item [hidden]="!canEdit || !event || !event.canedit || event.deleted" [priority]="300"
-                    [content]="'core.edit' | translate" (action)="openEdit()" iconAction="fas-edit">
+                <core-context-menu-item [hidden]="!event || !event.canedit || event.deleted || (!canEdit && event.id > 0)"
+                    [priority]="300" [content]="'core.edit' | translate" (action)="openEdit()" iconAction="fas-edit">
                 </core-context-menu-item>
                 <core-context-menu-item [hidden]="!event || !event.candelete || event.deleted" [priority]="200"
                     [content]="'core.delete' | translate" (action)="deleteEvent()"
@@ -123,34 +123,26 @@
                 </ion-label>
             </ion-item>
             <ng-container *ngFor="let reminder of reminders">
-                <ion-item *ngIf="reminder.time > 0 || defaultTime > 0" class="ion-text-wrap"
-                    [class.item-dimmed]="(reminder.time == -1 ? (event.timestart - defaultTime) : reminder.time) <= currentTime!">
+                <ion-item *ngIf="reminder.timestamp > 0" class="ion-text-wrap"
+                    [class.item-dimmed]="reminder.timestamp <= currentTime">
                     <ion-label>
-                        <p *ngIf="reminder.time == -1">
-                            {{ 'core.defaultvalue' | translate :{$a: ((event.timestart - defaultTime) * 1000) | coreFormatDate } }}
-                        </p>
-                        <p *ngIf="reminder.time > 0">{{ reminder.time * 1000 | coreFormatDate }}</p>
+                        <p>{{ reminder.label }}</p>
                     </ion-label>
                     <ion-button fill="clear" (click)="cancelNotification(reminder.id, $event)"
-                        [attr.aria-label]="'core.delete' | translate" slot="end"
-                        *ngIf="(reminder.time == -1 ? (event.timestart - defaultTime) : reminder.time) > currentTime!">
+                        [attr.aria-label]="'core.delete' | translate" slot="end" *ngIf="reminder.timestamp > currentTime">
                         <ion-icon name="fas-trash" color="danger" slot="icon-only" aria-hidden="true"></ion-icon>
                     </ion-button>
                 </ion-item>
             </ng-container>
 
-            <ng-container *ngIf="event.timestart + event.timeduration > currentTime!">
+            <ng-container *ngIf="event.timestart > currentTime">
                 <ion-item>
                     <ion-label>
-                        <ion-button expand="block" color="primary" (click)="notificationPicker.open()">
+                        <ion-button expand="block" color="primary" (click)="addReminder()">
                             {{ 'addon.calendar.setnewreminder' | translate }}
                         </ion-button>
                     </ion-label>
                 </ion-item>
-                <ion-datetime #notificationPicker hidden [(ngModel)]="notificationTimeText"
-                    [displayFormat]="notificationFormat" [min]="notificationMin" [max]="notificationMax"
-                    [doneText]="'core.add' | translate" (ionChange)="addNotificationTime()" [monthNames]="monthNames">
-                </ion-datetime>
             </ng-container>
         </ion-card>
     </core-loading>
diff --git a/src/addons/calendar/pages/event/event.page.ts b/src/addons/calendar/pages/event/event.page.ts
index 9ddc41f58..ac44adc68 100644
--- a/src/addons/calendar/pages/event/event.page.ts
+++ b/src/addons/calendar/pages/event/event.page.ts
@@ -20,7 +20,7 @@ import {
     AddonCalendarEventToDisplay,
     AddonCalendarProvider,
 } from '../../services/calendar';
-import { AddonCalendarHelper } from '../../services/calendar-helper';
+import { AddonCalendarEventReminder, AddonCalendarHelper } from '../../services/calendar-helper';
 import { AddonCalendarOffline } from '../../services/calendar-offline';
 import { AddonCalendarSync, AddonCalendarSyncEvents, AddonCalendarSyncProvider } from '../../services/calendar-sync';
 import { CoreApp } from '@services/app';
@@ -36,10 +36,9 @@ import { Network, NgZone, Translate } from '@singletons';
 import { Subscription } from 'rxjs';
 import { CoreNavigator } from '@services/navigator';
 import { CoreUtils } from '@services/utils/utils';
-import { AddonCalendarReminderDBRecord } from '../../services/database/calendar';
 import { ActivatedRoute } from '@angular/router';
 import { CoreConstants } from '@/core/constants';
-import { CoreLang } from '@services/lang';
+import { AddonCalendarReminderTimeModalComponent } from '@addons/calendar/components/reminder-time-modal/reminder-time-modal';
 
 /**
  * Page that displays a single calendar event.
@@ -53,17 +52,16 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
 
     protected eventId!: number;
     protected siteHomeId: number;
+    protected newEventObserver: CoreEventObserver;
     protected editEventObserver: CoreEventObserver;
     protected syncObserver: CoreEventObserver;
     protected manualSyncObserver: CoreEventObserver;
     protected onlineObserver: Subscription;
+    protected defaultTimeChangedObserver: CoreEventObserver;
     protected currentSiteId: string;
+    protected updateCurrentTime?: number;
 
     eventLoaded = false;
-    notificationFormat?: string;
-    notificationMin?: string;
-    notificationMax?: string;
-    notificationTimeText?: string;
     event?: AddonCalendarEventToDisplay;
     courseId?: number;
     courseName = '';
@@ -72,19 +70,16 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
     notificationsEnabled = false;
     moduleUrl = '';
     categoryPath = '';
-    currentTime?: number;
-    defaultTime = 0;
-    reminders: AddonCalendarReminderDBRecord[] = [];
+    currentTime = -1;
+    reminders: AddonCalendarEventReminder[] = [];
     canEdit = false;
     hasOffline = false;
     isOnline = false;
     syncIcon = CoreConstants.ICON_LOADING; // Sync icon.
-    monthNames?: string[];
 
     constructor(
         protected route: ActivatedRoute,
     ) {
-
         this.notificationsEnabled = CoreLocalNotifications.isAvailable();
         this.siteHomeId = CoreSites.getCurrentSiteHomeId();
         this.currentSiteId = CoreSites.getCurrentSiteId();
@@ -94,7 +89,16 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
 
         // Listen for event edited. If current event is edited, reload the data.
         this.editEventObserver = CoreEvents.on(AddonCalendarProvider.EDIT_EVENT_EVENT, (data) => {
-            if (data && data.eventId == this.eventId) {
+            if (data && data.eventId === this.eventId) {
+                this.eventLoaded = false;
+                this.refreshEvent(true, false);
+            }
+        }, this.currentSiteId);
+
+        // Listen for event created. If user edits the data of a new offline event or it's sent to server, this event is triggered.
+        this.newEventObserver = CoreEvents.on(AddonCalendarProvider.NEW_EVENT_EVENT, (data) => {
+            if (this.eventId < 0 && data && (data.eventId === this.eventId || data.oldEventId === this.eventId)) {
+                this.eventId = data.eventId;
                 this.eventLoaded = false;
                 this.refreshEvent(true, false);
             }
@@ -121,21 +125,35 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
                 this.isOnline = CoreApp.isOnline();
             });
         });
+
+        // Reload reminders if default notification time changes.
+        this.defaultTimeChangedObserver = CoreEvents.on(AddonCalendarProvider.DEFAULT_NOTIFICATION_TIME_CHANGED, () => {
+            this.loadReminders();
+
+            if (this.event) {
+                AddonCalendar.scheduleEventsNotifications([this.event]);
+            }
+        }, this.currentSiteId);
+
+        // Set and update current time. Use a 5 seconds error margin.
+        this.currentTime = CoreTimeUtils.timestamp();
+        this.updateCurrentTime = window.setInterval(() => {
+            this.currentTime = CoreTimeUtils.timestamp();
+        }, 5000);
     }
 
-    protected async initReminders(): Promise<void> {
-        if (this.notificationsEnabled) {
-            this.monthNames = CoreLang.getMonthNames();
-
-            this.reminders = await AddonCalendar.getEventReminders(this.eventId);
-            this.defaultTime = await AddonCalendar.getDefaultNotificationTime() * 60;
-
-            // Calculate format to use.
-            this.notificationFormat =
-                CoreTimeUtils.fixFormatForDatetime(CoreTimeUtils.convertPHPToMoment(
-                    Translate.instant('core.strftimedatetime'),
-                ));
+    /**
+     * Load reminders.
+     *
+     * @return Promise resolved when done.
+     */
+    protected async loadReminders(): Promise<void> {
+        if (!this.notificationsEnabled || !this.event) {
+            return;
         }
+
+        const reminders = await AddonCalendar.getEventReminders(this.eventId, this.currentSiteId);
+        this.reminders = await AddonCalendarHelper.formatReminders(reminders, this.event.timestart, this.currentSiteId);
     }
 
     /**
@@ -155,7 +173,6 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
         this.syncIcon = CoreConstants.ICON_LOADING;
 
         this.fetchEvent();
-        this.initReminders();
     }
 
     /**
@@ -166,48 +183,22 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
      * @return Promise resolved when done.
      */
     async fetchEvent(sync = false, showErrors = false): Promise<void> {
-        let deleted = false;
-
         this.isOnline = CoreApp.isOnline();
 
         if (sync) {
-            // Try to synchronize offline events.
-            try {
-                const result = await AddonCalendarSync.syncEvents();
-                if (result.warnings && result.warnings.length) {
-                    CoreDomUtils.showErrorModal(result.warnings[0]);
-                }
+            const deleted = await this.syncEvents(showErrors);
 
-                if (result.deleted && result.deleted.indexOf(this.eventId) != -1) {
-                    // This event was deleted during the sync.
-                    deleted = true;
-                }
-
-                if (result.updated) {
-                    // Trigger a manual sync event.
-                    result.source = 'event';
-
-                    CoreEvents.trigger(
-                        AddonCalendarSyncProvider.MANUAL_SYNCED,
-                        result,
-                        this.currentSiteId,
-                    );
-                }
-            } catch (error) {
-                if (showErrors) {
-                    CoreDomUtils.showErrorModalDefault(error, 'core.errorsync', true);
-                }
+            if (deleted) {
+                return;
             }
         }
 
-        if (deleted) {
-            return;
-        }
-
         try {
             // Get the event data.
-            const event = await AddonCalendar.getEventById(this.eventId);
-            this.event = await AddonCalendarHelper.formatEventData(event);
+            if (this.eventId >= 0) {
+                const event = await AddonCalendar.getEventById(this.eventId);
+                this.event = await AddonCalendarHelper.formatEventData(event);
+            }
 
             try {
                 const offlineEvent = AddonCalendarHelper.formatOfflineEventData(
@@ -216,20 +207,27 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
 
                 // There is offline data, apply it.
                 this.hasOffline = true;
-
-                this.event = Object.assign(this.event, offlineEvent);
+                this.event = Object.assign(this.event || {}, offlineEvent);
             } catch {
                 // No offline data.
                 this.hasOffline = false;
+
+                if (this.eventId < 0) {
+                    // It's an offline event, but it wasn't found. Shouldn't happen.
+                    CoreDomUtils.showErrorModal('Event not found.');
+                    CoreNavigator.back();
+
+                    return;
+                }
             }
 
-            this.currentTime = CoreTimeUtils.timestamp();
-            this.notificationMin = CoreTimeUtils.userDate(this.currentTime * 1000, 'YYYY-MM-DDTHH:mm', false);
-            this.notificationMax = CoreTimeUtils.userDate(
-                (this.event!.timestart + this.event!.timeduration) * 1000,
-                'YYYY-MM-DDTHH:mm',
-                false,
-            );
+            if (!this.event) {
+                return; // At this point we should always have the event, adding this check to avoid TS errors.
+            }
+
+            // Load reminders, and re-schedule them if needed (maybe the event time has changed).
+            this.loadReminders();
+            AddonCalendar.scheduleEventsNotifications([this.event]);
 
             // Reset some of the calculated data.
             this.categoryPath = '';
@@ -237,18 +235,19 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
             this.courseUrl = '';
             this.moduleUrl = '';
 
-            if (this.event!.moduleIcon) {
+            if (this.event.moduleIcon) {
                 // It's a module event, translate the module name to the current language.
-                const name = CoreCourse.translateModuleName(this.event!.modulename || '');
+                const name = CoreCourse.translateModuleName(this.event.modulename || '');
                 if (name.indexOf('core.mod_') === -1) {
-                    this.event!.modulename = name;
+                    this.event.modulename = name;
                 }
 
                 // Get the module URL.
-                this.moduleUrl = this.event!.url || '';
+                this.moduleUrl = this.event.url || '';
             }
 
             const promises: Promise<void>[] = [];
+            const event = this.event;
 
             const courseId = this.event.courseid;
             if (courseId != this.siteHomeId) {
@@ -262,16 +261,7 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
 
             // If it's a group event, get the name of the group.
             if (courseId && this.event.groupid) {
-                promises.push(CoreGroups.getUserGroupsInCourse(courseId).then((groups) => {
-                    const group = groups.find((group) => group.id == this.event!.groupid);
-
-                    this.groupName = group ? group.name : '';
-
-                    return;
-                }).catch(() => {
-                    // Error getting groups, just don't show the group name.
-                    this.groupName = '';
-                }));
+                promises.push(this.loadGroupName(this.event, courseId));
             }
 
             if (this.event.iscategoryevent && this.event.category) {
@@ -286,14 +276,14 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
 
             // Check if event was deleted in offine.
             promises.push(AddonCalendarOffline.isEventDeleted(this.eventId).then((deleted) => {
-                this.event!.deleted = deleted;
+                event.deleted = deleted;
 
                 return;
             }));
 
             // Re-calculate the formatted time so it uses the device date.
             promises.push(AddonCalendar.getCalendarTimeFormat().then(async (timeFormat) => {
-                this.event!.formattedtime = await AddonCalendar.formatEventTime(this.event!, timeFormat);
+                event.formattedtime = await AddonCalendar.formatEventTime(event, timeFormat);
 
                 return;
             }));
@@ -308,24 +298,88 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
     }
 
     /**
-     * Add a reminder for this event.
+     * Sync offline events.
+     *
+     * @param showErrors Whether to show sync errors to the user.
+     * @return Promise resolved with boolean: whether event was deleted on sync.
      */
-    async addNotificationTime(): Promise<void> {
-        if (this.notificationTimeText && this.event && this.event.id) {
-            let notificationTime = CoreTimeUtils.convertToTimestamp(this.notificationTimeText);
+    protected async syncEvents(showErrors = false): Promise<boolean> {
+        let deleted = false;
 
-            const currentTime = CoreTimeUtils.timestamp();
-            const minute = Math.floor(currentTime / 60) * 60;
-
-            // Check if the notification time is in the same minute as we are, so the notification is triggered.
-            if (notificationTime >= minute && notificationTime < minute + 60) {
-                notificationTime = currentTime + 1;
+        // Try to synchronize offline events.
+        try {
+            const result = await AddonCalendarSync.syncEvents();
+            if (result.warnings && result.warnings.length) {
+                CoreDomUtils.showErrorModal(result.warnings[0]);
             }
 
-            await AddonCalendar.addEventReminder(this.event, notificationTime);
-            this.reminders = await AddonCalendar.getEventReminders(this.eventId);
-            this.notificationTimeText = undefined;
+            if (result.deleted && result.deleted.indexOf(this.eventId) != -1) {
+                // This event was deleted during the sync.
+                deleted = true;
+            } else if (this.eventId < 0 && result.offlineIdMap[this.eventId]) {
+                // Event was created, use the online ID.
+                this.eventId = result.offlineIdMap[this.eventId];
+            }
+
+            if (result.updated) {
+                // Trigger a manual sync event.
+                result.source = 'event';
+
+                CoreEvents.trigger(
+                    AddonCalendarSyncProvider.MANUAL_SYNCED,
+                    result,
+                    this.currentSiteId,
+                );
+            }
+        } catch (error) {
+            if (showErrors) {
+                CoreDomUtils.showErrorModalDefault(error, 'core.errorsync', true);
+            }
         }
+
+        return deleted;
+    }
+
+    /**
+     * Load group name.
+     *
+     * @param event Event.
+     * @param courseId Course ID.
+     * @return Promise resolved when done.
+     */
+    protected async loadGroupName(event: AddonCalendarEventToDisplay, courseId: number): Promise<void> {
+        try {
+            const groups = await CoreGroups.getUserGroupsInCourse(courseId);
+
+            const group = groups.find((group) => group.id == event.groupid);
+            this.groupName = group ? group.name : '';
+
+        } catch {
+            // Error getting groups, just don't show the group name.
+            this.groupName = '';
+        }
+    }
+
+    /**
+     * Add a reminder for this event.
+     */
+    async addReminder(): Promise<void> {
+        if (!this.event || !this.event.id) {
+            return;
+        }
+
+        const reminderTime = await CoreDomUtils.openModal<number>({
+            component: AddonCalendarReminderTimeModalComponent,
+        });
+
+        if (reminderTime === undefined) {
+            // User canceled.
+            return;
+        }
+
+        await AddonCalendar.addEventReminder(this.event, reminderTime, this.currentSiteId);
+
+        await this.loadReminders();
     }
 
     /**
@@ -345,7 +399,7 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
 
             try {
                 await AddonCalendar.deleteEventReminder(id);
-                this.reminders = await AddonCalendar.getEventReminders(this.eventId);
+                await this.loadReminders();
             } catch (error) {
                 CoreDomUtils.showErrorModalDefault(error, 'Error deleting reminder');
             } finally {
@@ -387,7 +441,9 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
 
         const promises: Promise<void>[] = [];
 
-        promises.push(AddonCalendar.invalidateEvent(this.eventId));
+        if (this.eventId > 0) {
+            promises.push(AddonCalendar.invalidateEvent(this.eventId));
+        }
         promises.push(AddonCalendar.invalidateTimeFormat());
 
         await CoreUtils.allPromisesIgnoringErrors(promises);
@@ -454,9 +510,14 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
         const modal = await CoreDomUtils.showModalLoading('core.sending', true);
 
         try {
-            const sent = await AddonCalendar.deleteEvent(this.event.id, this.event.name, deleteAll);
+            let onlineEventDeleted = false;
+            if (this.event.id < 0) {
+                await AddonCalendarOffline.deleteEvent(this.event.id);
+            } else {
+                onlineEventDeleted = await AddonCalendar.deleteEvent(this.event.id, this.event.name, deleteAll);
+            }
 
-            if (sent) {
+            if (onlineEventDeleted) {
                 // Event deleted, invalidate right days & months.
                 try {
                     await AddonCalendarHelper.refreshAfterChangeEvent(this.event, deleteAll ? this.event.eventcount : 1);
@@ -466,12 +527,16 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
             }
 
             // Trigger an event.
-            CoreEvents.trigger(AddonCalendarProvider.DELETED_EVENT_EVENT, {
-                eventId: this.eventId,
-                sent: sent,
-            }, CoreSites.getCurrentSiteId());
+            if (this.event.id < 0) {
+                CoreEvents.trigger(AddonCalendarProvider.NEW_EVENT_DISCARDED_EVENT, {}, CoreSites.getCurrentSiteId());
+            } else {
+                CoreEvents.trigger(AddonCalendarProvider.DELETED_EVENT_EVENT, {
+                    eventId: this.eventId,
+                    sent: onlineEventDeleted,
+                }, CoreSites.getCurrentSiteId());
+            }
 
-            if (sent) {
+            if (onlineEventDeleted || this.event.id < 0) {
                 CoreDomUtils.showToast('addon.calendar.eventcalendareventdeleted', true, 3000);
 
                 // Event deleted, close the view.
@@ -532,11 +597,21 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
             // Event was deleted, close the view.
             CoreNavigator.back();
         } else if (data.events && (!isManual || data.source != 'event')) {
-            const event = data.events.find((ev) => ev.id == this.eventId);
+            if (this.eventId < 0) {
+                if (data.offlineIdMap[this.eventId]) {
+                    // Event was created, use the online ID.
+                    this.eventId = data.offlineIdMap[this.eventId];
 
-            if (event) {
-                this.eventLoaded = false;
-                this.refreshEvent();
+                    this.eventLoaded = false;
+                    this.refreshEvent();
+                }
+            } else {
+                const event = data.events.find((ev) => ev.id == this.eventId);
+
+                if (event) {
+                    this.eventLoaded = false;
+                    this.refreshEvent();
+                }
             }
         }
     }
@@ -545,10 +620,12 @@ export class AddonCalendarEventPage implements OnInit, OnDestroy {
      * Page destroyed.
      */
     ngOnDestroy(): void {
-        this.editEventObserver?.off();
-        this.syncObserver?.off();
-        this.manualSyncObserver?.off();
-        this.onlineObserver?.unsubscribe();
+        this.editEventObserver.off();
+        this.syncObserver.off();
+        this.manualSyncObserver.off();
+        this.onlineObserver.unsubscribe();
+        this.newEventObserver.off();
+        clearInterval(this.updateCurrentTime);
     }
 
 }
diff --git a/src/addons/calendar/pages/index/index.page.ts b/src/addons/calendar/pages/index/index.page.ts
index 7e4f1eeb2..f2c8fb51b 100644
--- a/src/addons/calendar/pages/index/index.page.ts
+++ b/src/addons/calendar/pages/index/index.page.ts
@@ -301,12 +301,7 @@ export class AddonCalendarIndexPage implements OnInit, OnDestroy {
      * @param eventId Event to load.
      */
     gotoEvent(eventId: number): void {
-        if (eventId < 0) {
-            // It's an offline event, go to the edit page.
-            this.openEdit(eventId);
-        } else {
-            CoreNavigator.navigateToSitePath(`/calendar/event/${eventId}`);
-        }
+        CoreNavigator.navigateToSitePath(`/calendar/event/${eventId}`);
     }
 
     /**
diff --git a/src/addons/calendar/pages/settings/settings.html b/src/addons/calendar/pages/settings/settings.html
index 8cc5f6dee..8ebb4f579 100644
--- a/src/addons/calendar/pages/settings/settings.html
+++ b/src/addons/calendar/pages/settings/settings.html
@@ -8,18 +8,10 @@
 </ion-header>
 <ion-content>
     <ion-list>
-        <ion-item *ngIf="defaultTime != -1">
+        <ion-item *ngIf="defaultTimeLabel">
             <ion-label>{{ 'addon.calendar.defaultnotificationtime' | translate }}</ion-label>
-            <ion-select [(ngModel)]="defaultTime" (ionChange)="updateDefaultTime(defaultTime)" interface="action-sheet"
-                [interfaceOptions]="{header: 'addon.calendar.defaultnotificationtime' | translate}">
-                <ion-select-option [value]="0">{{ 'core.settings.disabled' | translate }}</ion-select-option>
-                <ion-select-option [value]="10">{{ 600 | coreDuration }}</ion-select-option>
-                <ion-select-option [value]="30">{{ 1800 | coreDuration }}</ion-select-option>
-                <ion-select-option [value]="60">{{ 3600 | coreDuration }}</ion-select-option>
-                <ion-select-option [value]="120">{{ 7200 | coreDuration }}</ion-select-option>
-                <ion-select-option [value]="360">{{ 21600 | coreDuration }}</ion-select-option>
-                <ion-select-option [value]="720">{{ 43200 | coreDuration }}</ion-select-option>
-                <ion-select-option [value]="1440">{{ 86400 | coreDuration }}</ion-select-option>
+            <ion-select [(ngModel)]="defaultTimeLabel" (click)="changeDefaultTime($event)">
+                <ion-select-option [value]="defaultTimeLabel">{{ defaultTimeLabel }}</ion-select-option>
             </ion-select>
         </ion-item>
     </ion-list>
diff --git a/src/addons/calendar/pages/settings/settings.ts b/src/addons/calendar/pages/settings/settings.ts
index a42184f2d..ec1ee3455 100644
--- a/src/addons/calendar/pages/settings/settings.ts
+++ b/src/addons/calendar/pages/settings/settings.ts
@@ -13,9 +13,16 @@
 // limitations under the License.
 
 import { Component, OnInit } from '@angular/core';
-import { AddonCalendar, AddonCalendarProvider } from '../../services/calendar';
+import {
+    AddonCalendar,
+    AddonCalendarProvider,
+    AddonCalendarReminderUnits,
+    AddonCalendarValueAndUnit,
+} from '../../services/calendar';
 import { CoreEvents } from '@singletons/events';
 import { CoreSites } from '@services/sites';
+import { CoreDomUtils } from '@services/utils/dom';
+import { AddonCalendarReminderTimeModalComponent } from '@addons/calendar/components/reminder-time-modal/reminder-time-modal';
 
 /**
  * Page that displays the calendar settings.
@@ -26,13 +33,51 @@ import { CoreSites } from '@services/sites';
 })
 export class AddonCalendarSettingsPage implements OnInit {
 
-    defaultTime = -1;
+    defaultTimeLabel = '';
+
+    protected defaultTime: AddonCalendarValueAndUnit = {
+        value: 0,
+        unit: AddonCalendarReminderUnits.MINUTE,
+    };
 
     /**
      * View loaded.
      */
     async ngOnInit(): Promise<void> {
-        this.defaultTime = await AddonCalendar.getDefaultNotificationTime();
+        const defaultTime = await AddonCalendar.getDefaultNotificationTime();
+
+        this.defaultTime = AddonCalendarProvider.convertSecondsToValueAndUnit(defaultTime);
+        this.defaultTimeLabel = AddonCalendar.getUnitValueLabel(this.defaultTime.value, this.defaultTime.unit);
+    }
+
+    /**
+     * Change default time.
+     *
+     * @param e Event.
+     * @return Promise resolved when done.
+     */
+    async changeDefaultTime(e: Event): Promise<void> {
+        e.stopPropagation();
+        e.stopImmediatePropagation();
+        e.preventDefault();
+
+        const reminderTime = await CoreDomUtils.openModal<number>({
+            component: AddonCalendarReminderTimeModalComponent,
+            componentProps: {
+                initialValue: this.defaultTime,
+                allowDisable: true,
+            },
+        });
+
+        if (reminderTime === undefined) {
+            // User canceled.
+            return;
+        }
+
+        this.defaultTime = AddonCalendarProvider.convertSecondsToValueAndUnit(reminderTime);
+        this.defaultTimeLabel = AddonCalendar.getUnitValueLabel(this.defaultTime.value, this.defaultTime.unit);
+
+        this.updateDefaultTime(reminderTime);
     }
 
     /**
diff --git a/src/addons/calendar/services/calendar-helper.ts b/src/addons/calendar/services/calendar-helper.ts
index 447745701..d441b1c1d 100644
--- a/src/addons/calendar/services/calendar-helper.ts
+++ b/src/addons/calendar/services/calendar-helper.ts
@@ -23,6 +23,7 @@ import {
     AddonCalendarEventType,
     AddonCalendarGetEventsEvent,
     AddonCalendarProvider,
+    AddonCalendarReminderUnits,
     AddonCalendarWeek,
     AddonCalendarWeekDay,
 } from './calendar';
@@ -35,6 +36,7 @@ import { makeSingleton } from '@singletons';
 import { AddonCalendarSyncInvalidateEvent } from './calendar-sync';
 import { AddonCalendarOfflineEventDBRecord } from './database/calendar-offline';
 import { CoreCategoryData } from '@features/courses/services/courses';
+import { AddonCalendarReminderDBRecord } from './database/calendar';
 
 /**
  * Context levels enumeration.
@@ -220,7 +222,7 @@ export class AddonCalendarHelperProvider {
     formatOfflineEventData(event: AddonCalendarOfflineEventDBRecord): AddonCalendarEventToDisplay {
 
         const eventFormatted: AddonCalendarEventToDisplay = {
-            id: event.id!,
+            id: event.id,
             name: event.name,
             timestart: event.timestart,
             eventtype: event.eventtype,
@@ -243,6 +245,8 @@ export class AddonCalendarHelperProvider {
             format: 1,
             visible: 1,
             offline: true,
+            canedit: event.id < 0,
+            candelete: event.id < 0,
             timeduration: 0,
         };
 
@@ -282,6 +286,55 @@ export class AddonCalendarHelperProvider {
         }
     }
 
+    /**
+     * Format reminders, adding calculated data.
+     *
+     * @param reminders Reminders.
+     * @param timestart Event timestart.
+     * @param siteId Site ID.
+     * @return Formatted reminders.
+     */
+    async formatReminders(
+        reminders: AddonCalendarReminderDBRecord[],
+        timestart: number,
+        siteId?: string,
+    ): Promise<AddonCalendarEventReminder[]> {
+        const defaultTime = await AddonCalendar.getDefaultNotificationTime(siteId);
+
+        const formattedReminders = <AddonCalendarEventReminder[]> reminders;
+        const eventTimestart = timestart;
+        let defaultTimeValue: number | undefined;
+        let defaultTimeUnit: AddonCalendarReminderUnits | undefined;
+
+        if (defaultTime > 0) {
+            const data = AddonCalendarProvider.convertSecondsToValueAndUnit(defaultTime);
+            defaultTimeValue = data.value;
+            defaultTimeUnit = data.unit;
+        }
+
+        return formattedReminders.map((reminder) => {
+            if (reminder.time === null) {
+                // Default time. Check if default notifications are disabled.
+                if (defaultTimeValue !== undefined && defaultTimeUnit) {
+                    reminder.value = defaultTimeValue;
+                    reminder.unit = defaultTimeUnit;
+                    reminder.timestamp = eventTimestart - reminder.value * reminder.unit;
+                }
+            } else {
+                const data = AddonCalendarProvider.convertSecondsToValueAndUnit(reminder.time);
+                reminder.value = data.value;
+                reminder.unit = data.unit;
+                reminder.timestamp = eventTimestart - reminder.time;
+            }
+
+            if (reminder.value && reminder.unit) {
+                reminder.label = AddonCalendar.getUnitValueLabel(reminder.value, reminder.unit, reminder.time === null);
+            }
+
+            return reminder;
+        });
+    }
+
     /**
      * Get options (name & value) for each allowed event type.
      *
@@ -335,7 +388,7 @@ export class AddonCalendarHelperProvider {
         year: number,
         month: number,
         siteId?: string,
-    ): Promise<{ daynames: Partial<AddonCalendarDayName>[]; weeks: Partial<AddonCalendarWeek>[] }> {
+    ): Promise<{ daynames: Partial<AddonCalendarDayName>[]; weeks: AddonCalendarWeek[] }> {
         const site = await CoreSites.getSite(siteId);
         // Get starting week day user preference, fallback to site configuration.
         let startWeekDayStr = site.getStoredConfig('calendar_startwday');
@@ -344,7 +397,7 @@ export class AddonCalendarHelperProvider {
 
         const today = moment();
         const isCurrentMonth = today.year() == year && today.month() == month - 1;
-        const weeks: Partial<AddonCalendarWeek>[] = [];
+        const weeks: AddonCalendarWeek[] = [];
 
         let date = moment({ year, month: month - 1, date: 1 });
         for (let mday = 1; mday <= date.daysInMonth(); mday++) {
@@ -371,7 +424,7 @@ export class AddonCalendarHelperProvider {
             }
 
             // Add day to current week.
-            weeks[weeks.length - 1].days!.push({
+            weeks[weeks.length - 1].days.push({
                 events: [],
                 hasevents: false,
                 mday: date.date(),
@@ -450,11 +503,11 @@ export class AddonCalendarHelperProvider {
      */
     getFilteredEvents(
         events: AddonCalendarEventToDisplay[],
-        filter: AddonCalendarFilter,
+        filter: AddonCalendarFilter | undefined,
         categories: { [id: number]: CoreCategoryData },
     ): AddonCalendarEventToDisplay[] {
         // Do not filter.
-        if (!filter.filtered) {
+        if (!filter || !filter.filtered) {
             return events;
         }
 
@@ -475,9 +528,9 @@ export class AddonCalendarHelperProvider {
      * Check if an event should be displayed based on the filter.
      *
      * @param event Event object.
+     * @param categories Categories indexed by ID.
      * @param courseId Course ID to filter.
      * @param categoryId Category ID the course belongs to.
-     * @param categories Categories indexed by ID.
      * @return Whether it should be displayed.
      */
     protected shouldDisplayEvent(
@@ -492,7 +545,7 @@ export class AddonCalendarHelperProvider {
         }
 
         if (event.eventtype == 'category' && categories) {
-            if (!event.categoryid || !Object.keys(categories).length) {
+            if (!event.categoryid || !Object.keys(categories).length || !categoryId) {
                 // We can't tell if the course belongs to the category, display them all.
                 return true;
             }
@@ -503,7 +556,7 @@ export class AddonCalendarHelperProvider {
             }
 
             // Check parent categories.
-            let category = categories[categoryId!];
+            let category = categories[categoryId];
             while (category) {
                 if (!category.parent) {
                     // Category doesn't have parent, stop.
@@ -567,7 +620,7 @@ export class AddonCalendarHelperProvider {
                     await AddonCalendar.getLocalEventsByRepeatIdFromLocalDb(eventData.repeatid, site.id);
 
                 await CoreUtils.allPromises(repeatedEvents.map((event) =>
-                    AddonCalendar.invalidateEvent(event.id!)));
+                    AddonCalendar.invalidateEvent(event.id)));
 
                 return;
             }
@@ -670,7 +723,7 @@ export class AddonCalendarHelperProvider {
      */
     refreshAfterChangeEvent(
         event: {
-            id?: number;
+            id: number;
             repeatid?: number;
             timestart: number;
         },
@@ -679,7 +732,7 @@ export class AddonCalendarHelperProvider {
     ): Promise<void> {
         return this.refreshAfterChangeEvents(
             [{
-                id: event.id!,
+                id: event.id,
                 repeatid: event.repeatid,
                 timestart: event.timestart,
                 repeated: repeated,
@@ -725,3 +778,13 @@ export type AddonCalendarEventTypeOption = {
     name: string;
     value: AddonCalendarEventType;
 };
+
+/**
+ * Formatted event reminder.
+ */
+export type AddonCalendarEventReminder = AddonCalendarReminderDBRecord & {
+    value?: number; // Amount of time.
+    unit?: AddonCalendarReminderUnits; // Units.
+    timestamp?: number; // Timestamp (in seconds).
+    label?: string; // Label to represent the reminder.
+};
diff --git a/src/addons/calendar/services/calendar-offline.ts b/src/addons/calendar/services/calendar-offline.ts
index d34586f91..5d11344fa 100644
--- a/src/addons/calendar/services/calendar-offline.ts
+++ b/src/addons/calendar/services/calendar-offline.ts
@@ -110,7 +110,7 @@ export class AddonCalendarOfflineProvider {
     async getAllEditedEventsIds(siteId?: string): Promise<number[]> {
         const events = await this.getAllEditedEvents(siteId);
 
-        return events.map((event) => event.id!);
+        return events.map((event) => event.id);
     }
 
     /**
@@ -215,20 +215,18 @@ export class AddonCalendarOfflineProvider {
     /**
      * Offline version for adding a new discussion to a forum.
      *
-     * @param eventId Event ID. If it's a new event, set it to undefined/null.
+     * @param eventId Event ID. Negative value to edit offline event. If it's a new event, set it to undefined/null.
      * @param data Event data.
-     * @param timeCreated The time the event was created. If not defined, current time.
      * @param siteId Site ID. If not defined, current site.
      * @return Promise resolved with the stored event.
      */
     async saveEvent(
         eventId: number | undefined,
         data: AddonCalendarSubmitCreateUpdateFormDataWSParams,
-        timeCreated?: number,
         siteId?: string,
     ): Promise<AddonCalendarOfflineEventDBRecord> {
         const site = await CoreSites.getSite(siteId);
-        timeCreated = timeCreated || Date.now();
+        const timeCreated = Date.now();
         const event: AddonCalendarOfflineEventDBRecord = {
             id: eventId || -timeCreated,
             name: data.name,
diff --git a/src/addons/calendar/services/calendar-sync.ts b/src/addons/calendar/services/calendar-sync.ts
index 5d6fcad20..56f3e8a3c 100644
--- a/src/addons/calendar/services/calendar-sync.ts
+++ b/src/addons/calendar/services/calendar-sync.ts
@@ -100,9 +100,10 @@ export class AddonCalendarSyncProvider extends CoreSyncBaseProvider<AddonCalenda
     async syncEvents(siteId?: string): Promise<AddonCalendarSyncEvents> {
         siteId = siteId || CoreSites.getCurrentSiteId();
 
-        if (this.isSyncing(AddonCalendarSyncProvider.SYNC_ID, siteId)) {
+        const currentSyncPromise = this.getOngoingSync(AddonCalendarSyncProvider.SYNC_ID, siteId);
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this site, return the promise.
-            return this.getOngoingSync(AddonCalendarSyncProvider.SYNC_ID, siteId)!;
+            return currentSyncPromise;
         }
 
         this.logger.debug('Try to sync calendar events for site ' + siteId);
@@ -123,6 +124,7 @@ export class AddonCalendarSyncProvider extends CoreSyncBaseProvider<AddonCalenda
         const result: AddonCalendarSyncEvents = {
             warnings: [],
             events: [],
+            offlineIdMap: {},
             deleted: [],
             toinvalidate: [],
             updated: false,
@@ -255,10 +257,13 @@ export class AddonCalendarSyncProvider extends CoreSyncBaseProvider<AddonCalenda
         ); // Clone the object because it will be modified in the submit function.
 
         try {
-            const newEvent = await AddonCalendar.submitEventOnline(eventId > 0 ? eventId : 0, data, siteId);
+            const newEvent = await AddonCalendar.submitEventOnline(eventId, data, siteId);
 
             result.updated = true;
             result.events.push(newEvent);
+            if (eventId < 0) {
+                result.offlineIdMap[eventId] = newEvent.id;
+            }
 
             // Add data to invalidate.
             const numberOfRepetitions = data.repeat ? data.repeats :
@@ -272,7 +277,7 @@ export class AddonCalendarSyncProvider extends CoreSyncBaseProvider<AddonCalenda
             });
 
             // Event sent, delete the offline data.
-            return AddonCalendarOffline.deleteEvent(event.id!, siteId);
+            return AddonCalendarOffline.deleteEvent(event.id, siteId);
 
         } catch (error) {
             if (!CoreUtils.isWebServiceError(error)) {
@@ -283,7 +288,7 @@ export class AddonCalendarSyncProvider extends CoreSyncBaseProvider<AddonCalenda
             // The WebService has thrown an error, this means that the event cannot be created. Delete it.
             result.updated = true;
 
-            await AddonCalendarOffline.deleteEvent(event.id!, siteId);
+            await AddonCalendarOffline.deleteEvent(event.id, siteId);
 
             // Event deleted, add a warning.
             this.addOfflineDataDeletedWarning(result.warnings, event.name, error);
@@ -297,6 +302,7 @@ export const AddonCalendarSync = makeSingleton(AddonCalendarSyncProvider);
 export type AddonCalendarSyncEvents = {
     warnings: string[];
     events: AddonCalendarEvent[];
+    offlineIdMap: Record<number, number>; // Map offline ID with online ID for created events.
     deleted: number[];
     toinvalidate: AddonCalendarSyncInvalidateEvent[];
     updated: boolean;
diff --git a/src/addons/calendar/services/calendar.ts b/src/addons/calendar/services/calendar.ts
index f21f71869..815254572 100644
--- a/src/addons/calendar/services/calendar.ts
+++ b/src/addons/calendar/services/calendar.ts
@@ -53,6 +53,16 @@ export enum AddonCalendarEventType {
     USER = 'user',
 }
 
+/**
+ * Units to set a reminder.
+ */
+export enum AddonCalendarReminderUnits {
+    MINUTE = CoreConstants.SECONDS_MINUTE,
+    HOUR = CoreConstants.SECONDS_HOUR,
+    DAY = CoreConstants.SECONDS_DAY,
+    WEEK = CoreConstants.SECONDS_WEEK,
+}
+
 declare module '@singletons/events' {
 
     /**
@@ -72,6 +82,21 @@ declare module '@singletons/events' {
 
 }
 
+const REMINDER_UNITS_LABELS = {
+    single: {
+        [AddonCalendarReminderUnits.MINUTE]: 'core.minute',
+        [AddonCalendarReminderUnits.HOUR]: 'core.hour',
+        [AddonCalendarReminderUnits.DAY]: 'core.day',
+        [AddonCalendarReminderUnits.WEEK]: 'core.week',
+    },
+    multi: {
+        [AddonCalendarReminderUnits.MINUTE]: 'core.minutes',
+        [AddonCalendarReminderUnits.HOUR]: 'core.hours',
+        [AddonCalendarReminderUnits.DAY]: 'core.days',
+        [AddonCalendarReminderUnits.WEEK]: 'core.weeks',
+    },
+};
+
 /**
  * Service to handle calendar events.
  */
@@ -82,7 +107,7 @@ export class AddonCalendarProvider {
     static readonly COMPONENT = 'AddonCalendarEvents';
     static readonly DEFAULT_NOTIFICATION_TIME_CHANGED = 'AddonCalendarDefaultNotificationTimeChangedEvent';
     static readonly DEFAULT_NOTIFICATION_TIME_SETTING = 'mmaCalendarDefaultNotifTime';
-    static readonly DEFAULT_NOTIFICATION_TIME = 60;
+    static readonly DEFAULT_NOTIFICATION_TIME = 3600;
     static readonly STARTING_WEEK_DAY = 'addon_calendar_starting_week_day';
     static readonly NEW_EVENT_EVENT = 'addon_calendar_new_event';
     static readonly NEW_EVENT_DISCARDED_EVENT = 'addon_calendar_new_event_discarded';
@@ -156,6 +181,41 @@ export class AddonCalendarProvider {
         return !!site?.isVersionGreaterEqualThan('3.7.1');
     }
 
+    /**
+     * Given a number of seconds, convert it to a unit&value format compatible with reminders.
+     *
+     * @param seconds Number of seconds.
+     * @return Value and unit.
+     */
+    static convertSecondsToValueAndUnit(seconds: number): AddonCalendarValueAndUnit {
+        if (seconds <= 0) {
+            return {
+                value: 0,
+                unit: AddonCalendarReminderUnits.MINUTE,
+            };
+        } else if (seconds % AddonCalendarReminderUnits.WEEK === 0) {
+            return {
+                value: seconds / AddonCalendarReminderUnits.WEEK,
+                unit: AddonCalendarReminderUnits.WEEK,
+            };
+        } else if (seconds % AddonCalendarReminderUnits.DAY === 0) {
+            return {
+                value: seconds / AddonCalendarReminderUnits.DAY,
+                unit: AddonCalendarReminderUnits.DAY,
+            };
+        } else if (seconds % AddonCalendarReminderUnits.HOUR === 0) {
+            return {
+                value: seconds / AddonCalendarReminderUnits.HOUR,
+                unit: AddonCalendarReminderUnits.HOUR,
+            };
+        } else {
+            return {
+                value: seconds / AddonCalendarReminderUnits.MINUTE,
+                unit: AddonCalendarReminderUnits.MINUTE,
+            };
+        }
+    }
+
     /**
      * Delete an event.
      *
@@ -248,7 +308,7 @@ export class AddonCalendarProvider {
             REMINDERS_TABLE,
             { eventid: eventId },
         ).then((reminders) =>
-            Promise.all(reminders.map((reminder) => this.deleteEventReminder(reminder.id!, siteId)))));
+            Promise.all(reminders.map((reminder) => this.deleteEventReminder(reminder.id, siteId)))));
 
         try {
             await Promise.all(promises);
@@ -306,7 +366,7 @@ export class AddonCalendarProvider {
      */
     async formatEventTime(
         event: AddonCalendarEventToDisplay,
-        format: string,
+        format?: string,
         useCommonWords = true,
         seenDay?: number,
         showTime = 0,
@@ -548,7 +608,7 @@ export class AddonCalendarProvider {
      * Get the configured default notification time.
      *
      * @param siteId ID of the site. If not defined, use current site.
-     * @return Promise resolved with the default time.
+     * @return Promise resolved with the default time (in seconds).
      */
     async getDefaultNotificationTime(siteId?: string): Promise<number> {
         siteId = siteId || CoreSites.getCurrentSiteId();
@@ -656,18 +716,18 @@ export class AddonCalendarProvider {
         eventConverted.iscategoryevent = originalEvent.eventtype == AddonCalendarEventType.CATEGORY;
         eventConverted.normalisedeventtype = this.getEventType(recordAsRecord);
         try {
-            eventConverted.category = CoreTextUtils.parseJSON(recordAsRecord.category!);
+            eventConverted.category = CoreTextUtils.parseJSON(recordAsRecord.category || '');
         } catch {
             // Ignore errors.
         }
 
         try {
-            eventConverted.course = CoreTextUtils.parseJSON(recordAsRecord.course!);
+            eventConverted.course = CoreTextUtils.parseJSON(recordAsRecord.course || '');
         } catch {
             // Ignore errors.
         }
         try {
-            eventConverted.subscription = CoreTextUtils.parseJSON(recordAsRecord.subscription!);
+            eventConverted.subscription = CoreTextUtils.parseJSON(recordAsRecord.subscription || '');
         } catch {
             // Ignore errors.
         }
@@ -678,24 +738,27 @@ export class AddonCalendarProvider {
     /**
      * Adds an event reminder and schedule a new notification.
      *
-     * @param event Event to update its notification time.
-     * @param time New notification setting timestamp.
+     * @param event Event to set the reminder.
+     * @param time Amount of seconds of the reminder. Undefined for default reminder.
      * @param siteId ID of the site the event belongs to. If not defined, use current site.
      * @return Promise resolved when the notification is updated.
      */
     async addEventReminder(
-        event: { id: number; timestart: number; timeduration: number; name: string},
-        time: number,
+        event: { id: number; timestart: number; name: string},
+        time?: number | null,
         siteId?: string,
     ): Promise<void> {
         const site = await CoreSites.getSite(siteId);
-        const reminder: AddonCalendarReminderDBRecord = {
+        const reminder: Partial<AddonCalendarReminderDBRecord> = {
             eventid: event.id,
-            time: time,
+            time: time ?? null,
         };
+
         const reminderId = await site.getDb().insertRecord(REMINDERS_TABLE, reminder);
 
-        await this.scheduleEventNotification(event, reminderId, time, site.getId());
+        const timestamp = time ? event.timestart - time : time;
+
+        await this.scheduleEventNotification(event, reminderId, timestamp, site.getId());
     }
 
     /**
@@ -773,7 +836,7 @@ export class AddonCalendarProvider {
             preSets.emergencyCache = false;
         }
         const response: AddonCalendarCalendarDay = await site.read('core_calendar_get_calendar_day_view', params, preSets);
-        this.storeEventsInLocalDB(response.events, siteId);
+        this.storeEventsInLocalDB(response.events, { siteId });
 
         return response;
     }
@@ -855,6 +918,10 @@ export class AddonCalendarProvider {
         const start = initialTime + (CoreConstants.SECONDS_DAY * daysToStart);
         const end = start + (CoreConstants.SECONDS_DAY * daysInterval) - 1;
 
+        const events = {
+            courseids: <number[]> [],
+            groupids: <number[]> [],
+        };
         const params: AddonCalendarGetCalendarEventsWSParams = {
             options: {
                 userevents: true,
@@ -862,23 +929,20 @@ export class AddonCalendarProvider {
                 timestart: start,
                 timeend: end,
             },
-            events: {
-                courseids: [],
-                groupids: [],
-            },
+            events: events,
         };
 
         const promises: Promise<void>[] = [];
 
         promises.push(CoreCourses.getUserCourses(false, siteId).then((courses) => {
-            params.events!.courseids = courses.map((course) => course.id);
-            params.events!.courseids.push(site.getSiteHomeId()); // Add front page.
+            events.courseids = courses.map((course) => course.id);
+            events.courseids.push(site.getSiteHomeId()); // Add front page.
 
             return;
         }));
 
         promises.push(CoreGroups.getAllUserGroups(siteId).then((groups) => {
-            params.events!.groupids = groups.map((group) => group.id);
+            events.groupids = groups.map((group) => group.id);
 
             return;
         }));
@@ -976,7 +1040,7 @@ export class AddonCalendarProvider {
         const response = await site.read<AddonCalendarMonth>('core_calendar_get_calendar_monthly_view', params, preSets);
         response.weeks.forEach((week) => {
             week.days.forEach((day) => {
-                this.storeEventsInLocalDB(day.events as AddonCalendarCalendarEvent[], siteId);
+                this.storeEventsInLocalDB(day.events as AddonCalendarCalendarEvent[], { siteId });
             });
         });
 
@@ -1022,6 +1086,35 @@ export class AddonCalendarProvider {
                 (categoryId ? categoryId : '');
     }
 
+    /**
+     * Given a value and a unit, return the translated label.
+     *
+     * @param value Value.
+     * @param unit Unit.
+     * @param addDefaultLabel Whether to add the "Default" text.
+     * @return Translated label.
+     */
+    getUnitValueLabel(value: number, unit: AddonCalendarReminderUnits, addDefaultLabel = false): string {
+        if (value === 0) {
+            return Translate.instant('core.settings.disabled');
+        }
+
+        const unitsLabel = value === 1 ?
+            REMINDER_UNITS_LABELS.single[unit] :
+            REMINDER_UNITS_LABELS.multi[unit];
+
+        const label = Translate.instant('addon.calendar.timebefore', {
+            units: Translate.instant(unitsLabel),
+            value: value,
+        });
+
+        if (addDefaultLabel) {
+            return Translate.instant('core.defaultvalue', { $a: label });
+        }
+
+        return label;
+    }
+
     /**
      * Get upcoming calendar events.
      *
@@ -1060,7 +1153,7 @@ export class AddonCalendarProvider {
         }
 
         const response = await site.read<AddonCalendarUpcoming>('core_calendar_get_calendar_upcoming_view', params, preSets);
-        this.storeEventsInLocalDB(response.events, siteId);
+        this.storeEventsInLocalDB(response.events, { siteId });
 
         return response;
     }
@@ -1335,14 +1428,14 @@ export class AddonCalendarProvider {
      *
      * @param event Event to schedule.
      * @param reminderId The reminder ID.
-     * @param time Notification setting time (in minutes). E.g. 10 means "notificate 10 minutes before start".
+     * @param time Notification timestamp (in seconds). Undefined for default time.
      * @param siteId Site ID the event belongs to. If not defined, use current site.
      * @return Promise resolved when the notification is scheduled.
      */
     protected async scheduleEventNotification(
         event: { id: number; timestart: number; name: string},
         reminderId: number,
-        time: number,
+        time?: number | null,
         siteId?: string,
     ): Promise<void> {
 
@@ -1357,16 +1450,16 @@ export class AddonCalendarProvider {
             return CoreLocalNotifications.cancel(reminderId, AddonCalendarProvider.COMPONENT, siteId);
         }
 
-        if (time == -1) {
-            // If time is -1, get event default time to calculate the notification time.
+        if (!time) {
+            // Get event default time to calculate the notification time.
             time = await this.getDefaultNotificationTime(siteId);
 
-            if (time == 0) {
+            if (time === 0) {
                 // Default notification time is disabled, do not show.
                 return CoreLocalNotifications.cancel(reminderId, AddonCalendarProvider.COMPONENT, siteId);
             }
 
-            time = event.timestart - (time * 60);
+            time = event.timestart - time;
         }
 
         time = time * 1000;
@@ -1417,17 +1510,18 @@ export class AddonCalendarProvider {
         siteId = siteId || CoreSites.getCurrentSiteId();
 
         const promises = events.map(async (event) => {
-            const timeEnd = (event.timestart + event.timeduration) * 1000;
-
-            if (timeEnd <= new Date().getTime()) {
-                // The event has finished already, don't schedule it.
+            if (event.timestart * 1000 <= Date.now()) {
+                // The event has already started, don't schedule it.
                 return this.deleteLocalEvent(event.id, siteId);
             }
 
             const reminders = await this.getEventReminders(event.id, siteId);
 
-            const p2 = reminders.map((reminder: AddonCalendarReminderDBRecord) =>
-                this.scheduleEventNotification(event, (reminder.id!), reminder.time, siteId));
+            const p2 = reminders.map((reminder) => {
+                const time = reminder.time ? event.timestart - reminder.time : reminder.time;
+
+                return this.scheduleEventNotification(event, reminder.id, time, siteId);
+            });
 
             await Promise.all(p2);
         });
@@ -1454,20 +1548,29 @@ export class AddonCalendarProvider {
      * Store an event in local DB as it is.
      *
      * @param event Event to store.
-     * @param siteId ID of the site the event belongs to. If not defined, use current site.
+     * @param options Options.
      * @return Promise resolved when stored.
      */
-    async storeEventInLocalDb(event: AddonCalendarGetEventsEvent | AddonCalendarCalendarEvent, siteId?: string): Promise<void> {
-        const site = await CoreSites.getSite(siteId);
-        siteId = site.getId();
-        try {
-            await this.getEventFromLocalDb(event.id, site.id);
-        } catch {
-            // Event does not exist. Check if any reminder exists first.
-            const reminders = await this.getEventReminders(event.id, siteId);
+    protected async storeEventInLocalDb(
+        event: AddonCalendarGetEventsEvent | AddonCalendarCalendarEvent | AddonCalendarEvent,
+        options: AddonCalendarStoreEventsOptions = {},
+    ): Promise<void> {
+        const site = await CoreSites.getSite(options.siteId);
+        const siteId = site.getId();
+        const addDefaultReminder = options.addDefaultReminder ?? true;
 
-            if (reminders.length == 0) {
-                this.addEventReminder(event, -1, siteId);
+        if (addDefaultReminder) {
+            // Add default reminder if the event isn't stored already and doesn't have any reminder.
+            try {
+                await this.getEventFromLocalDb(event.id, siteId);
+            } catch {
+                // Event does not exist.
+                const reminders = await this.getEventReminders(event.id, siteId);
+
+                if (reminders.length === 0) {
+                    // No reminders, create the default one.
+                    this.addEventReminder(event, undefined, siteId);
+                }
             }
         }
 
@@ -1505,12 +1608,17 @@ export class AddonCalendarProvider {
                 viewurl: event.viewurl,
                 isactionevent: event.isactionevent ? 1 : 0,
                 url: event.url,
-                islastday: event.islastday ? 1 : 0,
-                popupname: event.popupname,
-                mindaytimestamp: event.mindaytimestamp,
-                maxdaytimestamp: event.maxdaytimestamp,
-                draggable: event.draggable ? 1 : 0,
             });
+
+            if ('islastday' in event) {
+                eventRecord = Object.assign(eventRecord, {
+                    islastday: event.islastday ? 1 : 0,
+                    popupname: event.popupname,
+                    mindaytimestamp: event.mindaytimestamp,
+                    maxdaytimestamp: event.maxdaytimestamp,
+                    draggable: event.draggable ? 1 : 0,
+                });
+            }
         } else if ('uuid' in event) {
             eventRecord = Object.assign(eventRecord, {
                 courseid: event.courseid,
@@ -1527,25 +1635,20 @@ export class AddonCalendarProvider {
      * Store events in local DB.
      *
      * @param events Events to store.
-     * @param siteId ID of the site the event belongs to. If not defined, use current site.
+     * @param options Options.
      * @return Promise resolved when the events are stored.
      */
     protected async storeEventsInLocalDB(
-        events: (AddonCalendarGetEventsEvent | AddonCalendarCalendarEvent)[],
-        siteId?: string,
+        events: (AddonCalendarGetEventsEvent | AddonCalendarCalendarEvent | AddonCalendarEvent)[],
+        options: AddonCalendarStoreEventsOptions = {},
     ): Promise<void> {
-        const site = await CoreSites.getSite(siteId);
-        siteId = site.getId();
-
-        await Promise.all(events.map((event: AddonCalendarGetEventsEvent| AddonCalendarCalendarEvent) =>
-            // If event does not exist on the DB, schedule the reminder.
-            this.storeEventInLocalDb(event, siteId)));
+        await Promise.all(events.map((event) => this.storeEventInLocalDb(event, options)));
     }
 
     /**
      * Submit a calendar event.
      *
-     * @param eventId ID of the event. If undefined/null, create a new event.
+     * @param eventId ID of the event. Negative value to edit offline event. If undefined/null, create a new event.
      * @param formData Form data.
      * @param timeCreated The time the event was created. Only if modifying a new offline event.
      * @param forceOffline True to always save it in offline.
@@ -1555,19 +1658,26 @@ export class AddonCalendarProvider {
     async submitEvent(
         eventId: number | undefined,
         formData: AddonCalendarSubmitCreateUpdateFormDataWSParams,
-        timeCreated?: number,
-        forceOffline = false,
-        siteId?: string,
+        options: AddonCalendarSubmitEventOptions = {},
     ): Promise<{sent: boolean; event: AddonCalendarOfflineEventDBRecord | AddonCalendarEvent}> {
 
-        siteId = siteId || CoreSites.getCurrentSiteId();
+        const siteId = options.siteId || CoreSites.getCurrentSiteId();
 
         // Function to store the event to be synchronized later.
-        const storeOffline = (): Promise<{ sent: boolean; event: AddonCalendarOfflineEventDBRecord }> =>
-            AddonCalendarOffline.saveEvent(eventId, formData, timeCreated, siteId).then((event) =>
-                ({ sent: false, event }));
+        const storeOffline = async (): Promise<{ sent: boolean; event: AddonCalendarOfflineEventDBRecord }> => {
+            const event = await AddonCalendarOffline.saveEvent(eventId, formData, siteId);
 
-        if (forceOffline || !CoreApp.isOnline()) {
+            // Now save the reminders if any.
+            if (options.reminders) {
+                await CoreUtils.ignoreErrors(
+                    Promise.all(options.reminders.map((reminder) => this.addEventReminder(event, reminder.time, siteId))),
+                );
+            }
+
+            return { sent: false, event };
+        };
+
+        if (options.forceOffline || !CoreApp.isOnline()) {
             // App is offline, store the event.
             return storeOffline();
         }
@@ -1579,6 +1689,13 @@ export class AddonCalendarProvider {
         try {
             const event = await this.submitEventOnline(eventId, formData, siteId);
 
+            // Now save the reminders if any.
+            if (options.reminders) {
+                await CoreUtils.ignoreErrors(
+                    Promise.all(options.reminders.map((reminder) => this.addEventReminder(event, reminder.time, siteId))),
+                );
+            }
+
             return ({ sent: true, event });
         } catch (error) {
             if (error && !CoreUtils.isWebServiceError(error)) {
@@ -1594,7 +1711,7 @@ export class AddonCalendarProvider {
     /**
      * Submit an event, either to create it or to edit it. It will fail if offline or cannot connect.
      *
-     * @param eventId ID of the event. If undefined/null, create a new event.
+     * @param eventId ID of the event. If undefined/null or negative number, create a new event.
      * @param formData Form data.
      * @param siteId Site ID. If not provided, current site.
      * @return Promise resolved when done.
@@ -1605,8 +1722,9 @@ export class AddonCalendarProvider {
         siteId?: string,
     ): Promise<AddonCalendarEvent> {
         const site = await CoreSites.getSite(siteId);
+
         // Add data that is "hidden" in web.
-        formData.id = eventId;
+        formData.id = eventId > 0 ? eventId : 0;
         formData.userid = site.getUserId();
         formData.visible = 1;
         formData.instance = 0;
@@ -1615,12 +1733,14 @@ export class AddonCalendarProvider {
         } else {
             formData['_qf__core_calendar_local_event_forms_create'] = 1;
         }
+
         const params: AddonCalendarSubmitCreateUpdateFormWSParams = {
             formdata: CoreUtils.objectToGetParams(formData),
         };
         const result =
             await site.write<AddonCalendarSubmitCreateUpdateFormWSResponse>('core_calendar_submit_create_update_form', params);
-        if (result.validationerror) {
+
+        if (result.validationerror || !result.event) {
             // Simulate a WS error.
             throw new CoreWSError({
                 message: Translate.instant('core.invalidformdata'),
@@ -1628,7 +1748,19 @@ export class AddonCalendarProvider {
             });
         }
 
-        return result.event!;
+        if (eventId < 0) {
+            // Offline event has been sent. Change reminders eventid if any.
+            await CoreUtils.ignoreErrors(
+                site.getDb().updateRecords(REMINDERS_TABLE, { eventid: result.event.id }, { eventid: eventId }),
+            );
+        }
+
+        if (formData.id === 0) {
+            // Store the new event in local DB.
+            await CoreUtils.ignoreErrors(this.storeEventInLocalDb(result.event, { addDefaultReminder: false, siteId }));
+        }
+
+        return result.event;
     }
 
 }
@@ -2088,7 +2220,8 @@ type AddonCalendarSubmitCreateUpdateFormWSParams = {
 /**
  * Form data on AddonCalendarSubmitCreateUpdateFormWSParams.
  */
-export type AddonCalendarSubmitCreateUpdateFormDataWSParams = Omit<AddonCalendarOfflineEventDBRecord, 'description'> & {
+export type AddonCalendarSubmitCreateUpdateFormDataWSParams = Omit<AddonCalendarOfflineEventDBRecord, 'id'|'description'> & {
+    id?: number;
     description?: {
         text: string;
         format: number;
@@ -2143,6 +2276,7 @@ export type AddonCalendarEventToDisplay = Partial<AddonCalendarCalendarEvent> &
  */
 export type AddonCalendarUpdatedEventEvent = {
     eventId: number;
+    oldEventId?: number; // Old event ID. Used when an offline event is sent.
     sent?: boolean;
 };
 
@@ -2154,3 +2288,30 @@ type AddonCalendarPushNotificationData = {
     reminderId: number;
     siteId: string;
 };
+
+/**
+ * Value and unit for reminders.
+ */
+export type AddonCalendarValueAndUnit = {
+    value: number;
+    unit: AddonCalendarReminderUnits;
+};
+
+/**
+ * Options to pass to submit event.
+ */
+export type AddonCalendarSubmitEventOptions = {
+    reminders?: {
+        time: number | null;
+    }[];
+    forceOffline?: boolean;
+    siteId?: string; // Site ID. If not defined, current site.
+};
+
+/**
+ * Options to pass to store events in local DB.
+ */
+export type AddonCalendarStoreEventsOptions = {
+    addDefaultReminder?: boolean; // Whether to add default reminder for new events with no reminders. Defaults to true.
+    siteId?: string; // Site ID. If not defined, current site.
+};
diff --git a/src/addons/calendar/services/database/calendar-offline.ts b/src/addons/calendar/services/database/calendar-offline.ts
index 046dc59f5..5e08f8378 100644
--- a/src/addons/calendar/services/database/calendar-offline.ts
+++ b/src/addons/calendar/services/database/calendar-offline.ts
@@ -135,7 +135,7 @@ export const CALENDAR_OFFLINE_SITE_SCHEMA: CoreSiteSchema = {
 };
 
 export type AddonCalendarOfflineEventDBRecord = {
-    id?: number; // Negative for offline entries.
+    id: number; // Negative for offline entries.
     name: string;
     timestart: number;
     eventtype: AddonCalendarEventType;
diff --git a/src/addons/calendar/services/database/calendar.ts b/src/addons/calendar/services/database/calendar.ts
index c6d3acd3d..9a890b79f 100644
--- a/src/addons/calendar/services/database/calendar.ts
+++ b/src/addons/calendar/services/database/calendar.ts
@@ -14,7 +14,8 @@
 
 import { SQLiteDB } from '@classes/sqlitedb';
 import { CoreSiteSchema } from '@services/sites';
-import { AddonCalendarEventType } from '../calendar';
+import { CoreUtils } from '@services/utils/utils';
+import { AddonCalendar, AddonCalendarEventType } from '../calendar';
 
 /**
  * Database variables for AddonDatabase service.
@@ -23,7 +24,7 @@ export const EVENTS_TABLE = 'addon_calendar_events_3';
 export const REMINDERS_TABLE = 'addon_calendar_reminders';
 export const CALENDAR_SITE_SCHEMA: CoreSiteSchema = {
     name: 'AddonCalendarProvider',
-    version: 3,
+    version: 4,
     canBeCleared: [EVENTS_TABLE],
     tables: [
         {
@@ -199,8 +200,9 @@ export const CALENDAR_SITE_SCHEMA: CoreSiteSchema = {
             ],
         },
     ],
-    async migrate(db: SQLiteDB, oldVersion: number): Promise<void> {
+    async migrate(db: SQLiteDB, oldVersion: number, siteId: string): Promise<void> {
         if (oldVersion < 3) {
+            // Migrate calendar events. New format @since 3.7.
             let oldTable = 'addon_calendar_events_2';
 
             try {
@@ -212,11 +214,51 @@ export const CALENDAR_SITE_SCHEMA: CoreSiteSchema = {
 
             await db.migrateTable(oldTable, EVENTS_TABLE);
         }
+
+        if (oldVersion < 4) {
+            // Migrate reminders. New format @since 4.0.
+            const defaultTime = await CoreUtils.ignoreErrors(AddonCalendar.getDefaultNotificationTime(siteId));
+            if (defaultTime) {
+                // Convert from minutes to seconds.
+                AddonCalendar.setDefaultNotificationTime(defaultTime * 60, siteId);
+            }
+
+            const records = await db.getAllRecords<AddonCalendarReminderDBRecord>(REMINDERS_TABLE);
+            const events: Record<number, AddonCalendarEventDBRecord> = {};
+
+            await Promise.all(records.map(async (record) => {
+                // Get the event to compare the reminder time with the event time.
+                if (!events[record.eventid]) {
+                    try {
+                        events[record.eventid] = await db.getRecord(EVENTS_TABLE, { id: record.eventid });
+                    } catch {
+                        // Event not found in local DB, shouldn't happen. Delete the reminder.
+                        await db.deleteRecords(REMINDERS_TABLE, { id: record.id });
+
+                        return;
+                    }
+                }
+
+                if (!record.time || record.time === -1) {
+                    // Default reminder. Use null now.
+                    record.time = null;
+                } else if (record.time > events[record.eventid].timestart) {
+                    // Reminder is after the event, delete it.
+                    await db.deleteRecords(REMINDERS_TABLE, { id: record.id });
+
+                    return;
+                } else {
+                    record.time = events[record.eventid].timestart - record.time;
+                }
+
+                return this.insertRecord(REMINDERS_TABLE, record);
+            }));
+        }
     },
 };
 
 export type AddonCalendarEventDBRecord = {
-    id?: number;
+    id: number;
     name: string;
     description: string;
     eventtype: AddonCalendarEventType;
@@ -257,7 +299,7 @@ export type AddonCalendarEventDBRecord = {
 };
 
 export type AddonCalendarReminderDBRecord = {
-    id?: number;
+    id: number;
     eventid: number;
-    time: number;
+    time: number | null; // Number of seconds before the event, null for default time.
 };
diff --git a/src/addons/messages/services/messages-sync.ts b/src/addons/messages/services/messages-sync.ts
index 9a29b9f7d..cdcc4dd6c 100644
--- a/src/addons/messages/services/messages-sync.ts
+++ b/src/addons/messages/services/messages-sync.ts
@@ -147,9 +147,10 @@ export class AddonMessagesSyncProvider extends CoreSyncBaseProvider<AddonMessage
 
         const syncId = this.getSyncId(conversationId, userId);
 
-        if (this.isSyncing(syncId, siteId)) {
+        const currentSyncPromise = this.getOngoingSync(syncId, siteId);
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this conversation, return the promise.
-            return this.getOngoingSync(syncId, siteId)!;
+            return currentSyncPromise;
         }
 
         return this.addOngoingSync(syncId, this.performSyncDiscussion(conversationId, userId, siteId), siteId);
diff --git a/src/addons/mod/assign/services/assign-sync.ts b/src/addons/mod/assign/services/assign-sync.ts
index e47429236..99420a9a1 100644
--- a/src/addons/mod/assign/services/assign-sync.ts
+++ b/src/addons/mod/assign/services/assign-sync.ts
@@ -163,9 +163,10 @@ export class AddonModAssignSyncProvider extends CoreCourseActivitySyncBaseProvid
     async syncAssign(assignId: number, siteId?: string): Promise<AddonModAssignSyncResult> {
         siteId = siteId || CoreSites.getCurrentSiteId();
 
-        if (this.isSyncing(assignId, siteId)) {
+        const currentSyncPromise = this.getOngoingSync(assignId, siteId);
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this assign, return the promise.
-            return this.getOngoingSync(assignId, siteId)!;
+            return currentSyncPromise;
         }
 
         // Verify that assign isn't blocked.
diff --git a/src/addons/mod/choice/services/choice-sync.ts b/src/addons/mod/choice/services/choice-sync.ts
index a27a01f05..ed2537467 100644
--- a/src/addons/mod/choice/services/choice-sync.ts
+++ b/src/addons/mod/choice/services/choice-sync.ts
@@ -122,9 +122,10 @@ export class AddonModChoiceSyncProvider extends CoreCourseActivitySyncBaseProvid
         siteId = site.getId();
 
         const syncId = this.getSyncId(choiceId, userId);
-        if (this.isSyncing(syncId, siteId)) {
+        const currentSyncPromise = this.getOngoingSync(syncId, siteId);
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this discussion, return the promise.
-            return this.getOngoingSync(syncId, siteId)!;
+            return currentSyncPromise;
         }
 
         this.logger.debug(`Try to sync choice '${choiceId}' for user '${userId}'`);
diff --git a/src/addons/mod/data/services/data-sync.ts b/src/addons/mod/data/services/data-sync.ts
index a010247c4..9a947ffcb 100644
--- a/src/addons/mod/data/services/data-sync.ts
+++ b/src/addons/mod/data/services/data-sync.ts
@@ -135,9 +135,10 @@ export class AddonModDataSyncProvider extends CoreCourseActivitySyncBaseProvider
     syncDatabase(dataId: number, siteId?: string): Promise<AddonModDataSyncResult> {
         siteId = siteId || CoreSites.getCurrentSiteId();
 
-        if (this.isSyncing(dataId, siteId)) {
+        const currentSyncPromise = this.getOngoingSync(dataId, siteId);
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this database, return the promise.
-            return this.getOngoingSync(dataId, siteId)!;
+            return currentSyncPromise;
         }
 
         // Verify that database isn't blocked.
diff --git a/src/addons/mod/feedback/services/feedback-sync.ts b/src/addons/mod/feedback/services/feedback-sync.ts
index d404ed6f2..8b6702b8a 100644
--- a/src/addons/mod/feedback/services/feedback-sync.ts
+++ b/src/addons/mod/feedback/services/feedback-sync.ts
@@ -130,9 +130,10 @@ export class AddonModFeedbackSyncProvider extends CoreCourseActivitySyncBaseProv
     syncFeedback(feedbackId: number, siteId?: string): Promise<AddonModFeedbackSyncResult> {
         siteId = siteId || CoreSites.getCurrentSiteId();
 
-        if (this.isSyncing(feedbackId, siteId)) {
+        const currentSyncPromise = this.getOngoingSync(feedbackId, siteId);
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this feedback, return the promise.
-            return this.getOngoingSync(feedbackId, siteId)!;
+            return currentSyncPromise;
         }
 
         // Verify that feedback isn't blocked.
diff --git a/src/addons/mod/forum/services/forum-sync.ts b/src/addons/mod/forum/services/forum-sync.ts
index fae896b0c..65925b3d7 100644
--- a/src/addons/mod/forum/services/forum-sync.ts
+++ b/src/addons/mod/forum/services/forum-sync.ts
@@ -198,10 +198,11 @@ export class AddonModForumSyncProvider extends CoreCourseActivitySyncBaseProvide
         siteId = siteId || CoreSites.getCurrentSiteId();
 
         const syncId = this.getForumSyncId(forumId, userId);
+        const currentSyncPromise = this.getOngoingSync(syncId, siteId);
 
-        if (this.isSyncing(syncId, siteId)) {
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this discussion, return the promise.
-            return this.getOngoingSync(syncId, siteId)!;
+            return currentSyncPromise;
         }
 
         // Verify that forum isn't blocked.
@@ -429,10 +430,11 @@ export class AddonModForumSyncProvider extends CoreCourseActivitySyncBaseProvide
         siteId = siteId || CoreSites.getCurrentSiteId();
 
         const syncId = this.getDiscussionSyncId(discussionId, userId);
+        const currentSyncPromise = this.getOngoingSync(syncId, siteId);
 
-        if (this.isSyncing(syncId, siteId)) {
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this discussion, return the promise.
-            return this.getOngoingSync(syncId, siteId)!;
+            return currentSyncPromise;
         }
 
         // Verify that forum isn't blocked.
diff --git a/src/addons/mod/glossary/services/glossary-sync.ts b/src/addons/mod/glossary/services/glossary-sync.ts
index 80a2fbe0d..8d0844cb4 100644
--- a/src/addons/mod/glossary/services/glossary-sync.ts
+++ b/src/addons/mod/glossary/services/glossary-sync.ts
@@ -144,9 +144,10 @@ export class AddonModGlossarySyncProvider extends CoreCourseActivitySyncBaseProv
         siteId = siteId || CoreSites.getCurrentSiteId();
 
         const syncId = this.getGlossarySyncId(glossaryId, userId);
-        if (this.isSyncing(syncId, siteId)) {
+        const currentSyncPromise = this.getOngoingSync(syncId, siteId);
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this glossary, return the promise.
-            return this.getOngoingSync(syncId, siteId)!;
+            return currentSyncPromise;
         }
 
         // Verify that glossary isn't blocked.
diff --git a/src/addons/mod/h5pactivity/services/h5pactivity-sync.ts b/src/addons/mod/h5pactivity/services/h5pactivity-sync.ts
index 10aeb200d..95b5748ca 100644
--- a/src/addons/mod/h5pactivity/services/h5pactivity-sync.ts
+++ b/src/addons/mod/h5pactivity/services/h5pactivity-sync.ts
@@ -108,9 +108,10 @@ export class AddonModH5PActivitySyncProvider extends CoreCourseActivitySyncBaseP
             throw new CoreNetworkError();
         }
 
-        if (this.isSyncing(contextId, siteId)) {
+        const currentSyncPromise = this.getOngoingSync(contextId, siteId);
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this discussion, return the promise.
-            return this.getOngoingSync(contextId, siteId)!;
+            return currentSyncPromise;
         }
 
         return this.addOngoingSync(contextId, this.syncActivityData(contextId, siteId), siteId);
diff --git a/src/addons/mod/quiz/services/quiz-sync.ts b/src/addons/mod/quiz/services/quiz-sync.ts
index 25c101242..6990384f1 100644
--- a/src/addons/mod/quiz/services/quiz-sync.ts
+++ b/src/addons/mod/quiz/services/quiz-sync.ts
@@ -263,9 +263,10 @@ export class AddonModQuizSyncProvider extends CoreCourseActivitySyncBaseProvider
     syncQuiz(quiz: AddonModQuizQuizWSData, askPreflight?: boolean, siteId?: string): Promise<AddonModQuizSyncResult> {
         siteId = siteId || CoreSites.getCurrentSiteId();
 
-        if (this.isSyncing(quiz.id, siteId)) {
+        const currentSyncPromise = this.getOngoingSync(quiz.id, siteId);
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this quiz, return the promise.
-            return this.getOngoingSync(quiz.id, siteId)!;
+            return currentSyncPromise;
         }
 
         // Verify that quiz isn't blocked.
diff --git a/src/addons/mod/scorm/services/scorm-sync.ts b/src/addons/mod/scorm/services/scorm-sync.ts
index 3ebcfec81..5c9e1f158 100644
--- a/src/addons/mod/scorm/services/scorm-sync.ts
+++ b/src/addons/mod/scorm/services/scorm-sync.ts
@@ -579,9 +579,10 @@ export class AddonModScormSyncProvider extends CoreCourseActivitySyncBaseProvide
     syncScorm(scorm: AddonModScormScorm, siteId?: string): Promise<AddonModScormSyncResult> {
         siteId = siteId || CoreSites.getCurrentSiteId();
 
-        if (this.isSyncing(scorm.id, siteId)) {
+        const currentSyncPromise = this.getOngoingSync(scorm.id, siteId);
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this SCORM, return the promise.
-            return this.getOngoingSync(scorm.id, siteId)!;
+            return currentSyncPromise;
         }
 
         // Verify that SCORM isn't blocked.
diff --git a/src/addons/mod/survey/services/survey-sync.ts b/src/addons/mod/survey/services/survey-sync.ts
index f9c70bf91..e128b0b1e 100644
--- a/src/addons/mod/survey/services/survey-sync.ts
+++ b/src/addons/mod/survey/services/survey-sync.ts
@@ -124,10 +124,11 @@ export class AddonModSurveySyncProvider extends CoreCourseActivitySyncBaseProvid
         userId = userId || site.getUserId();
 
         const syncId = this.getSyncId(surveyId, userId);
+        const currentSyncPromise = this.getOngoingSync(syncId, siteId);
 
-        if (this.isSyncing(syncId, siteId)) {
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this site, return the promise.
-            return this.getOngoingSync(syncId, siteId)!;
+            return currentSyncPromise;
         }
 
         this.logger.debug(`Try to sync survey '${surveyId}' for user '${userId}'`);
diff --git a/src/addons/mod/wiki/services/wiki-sync.ts b/src/addons/mod/wiki/services/wiki-sync.ts
index 691a08e9b..da3d9ae21 100644
--- a/src/addons/mod/wiki/services/wiki-sync.ts
+++ b/src/addons/mod/wiki/services/wiki-sync.ts
@@ -167,10 +167,11 @@ export class AddonModWikiSyncProvider extends CoreSyncBaseProvider<AddonModWikiS
         siteId = siteId || CoreSites.getCurrentSiteId();
 
         const subwikiBlockId = this.getSubwikiBlockId(subwikiId, wikiId, userId, groupId);
+        const currentSyncPromise = this.getOngoingSync(subwikiBlockId, siteId);
 
-        if (this.isSyncing(subwikiBlockId, siteId)) {
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this subwiki, return the promise.
-            return this.getOngoingSync(subwikiBlockId, siteId)!;
+            return currentSyncPromise;
         }
 
         // Verify that subwiki isn't blocked.
diff --git a/src/addons/mod/workshop/services/workshop-sync.ts b/src/addons/mod/workshop/services/workshop-sync.ts
index f156c3e36..da2ec1f73 100644
--- a/src/addons/mod/workshop/services/workshop-sync.ts
+++ b/src/addons/mod/workshop/services/workshop-sync.ts
@@ -129,9 +129,10 @@ export class AddonModWorkshopSyncProvider extends CoreSyncBaseProvider<AddonModW
     syncWorkshop(workshopId: number, siteId?: string): Promise<AddonModWorkshopSyncResult> {
         siteId = siteId || CoreSites.getCurrentSiteId();
 
-        if (this.isSyncing(workshopId, siteId)) {
+        const currentSyncPromise = this.getOngoingSync(workshopId, siteId);
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this discussion, return the promise.
-            return this.getOngoingSync(workshopId, siteId)!;
+            return currentSyncPromise;
         }
 
         // Verify that workshop isn't blocked.
diff --git a/src/addons/notes/services/notes-sync.ts b/src/addons/notes/services/notes-sync.ts
index a9dfac04d..218b18418 100644
--- a/src/addons/notes/services/notes-sync.ts
+++ b/src/addons/notes/services/notes-sync.ts
@@ -112,9 +112,10 @@ export class AddonNotesSyncProvider extends CoreSyncBaseProvider<AddonNotesSyncR
     syncNotes(courseId: number, siteId?: string): Promise<AddonNotesSyncResult> {
         siteId = siteId || CoreSites.getCurrentSiteId();
 
-        if (this.isSyncing(courseId, siteId)) {
+        const currentSyncPromise = this.getOngoingSync(courseId, siteId);
+        if (currentSyncPromise) {
             // There's already a sync ongoing for notes, return the promise.
-            return this.getOngoingSync(courseId, siteId)!;
+            return currentSyncPromise;
         }
 
         this.logger.debug('Try to sync notes for course ' + courseId);
diff --git a/src/core/classes/base-sync.ts b/src/core/classes/base-sync.ts
index 9c5fc0229..8849ec24c 100644
--- a/src/core/classes/base-sync.ts
+++ b/src/core/classes/base-sync.ts
@@ -105,7 +105,7 @@ export class CoreSyncBaseProvider<T = void> {
         try {
             return await promise;
         } finally {
-            delete this.syncPromises[siteId!][uniqueId];
+            delete this.syncPromises[siteId][uniqueId];
         }
     }
 
@@ -133,15 +133,11 @@ export class CoreSyncBaseProvider<T = void> {
      */
     getOngoingSync(id: string | number, siteId?: string): Promise<T> | undefined {
         siteId = siteId || CoreSites.getCurrentSiteId();
-
-        if (!this.isSyncing(id, siteId)) {
-            return;
-        }
-
-        // There's already a sync ongoing for this id, return the promise.
         const uniqueId = this.getUniqueSyncId(id);
 
-        return this.syncPromises[siteId][uniqueId];
+        if (this.syncPromises[siteId] && this.syncPromises[siteId][uniqueId] !== undefined) {
+            return this.syncPromises[siteId][uniqueId];
+        }
     }
 
     /**
@@ -223,11 +219,7 @@ export class CoreSyncBaseProvider<T = void> {
      * @return Whether it's synchronizing.
      */
     isSyncing(id: string | number, siteId?: string): boolean {
-        siteId = siteId || CoreSites.getCurrentSiteId();
-
-        const uniqueId = this.getUniqueSyncId(id);
-
-        return !!(this.syncPromises[siteId] && this.syncPromises[siteId][uniqueId]);
+        return !!this.getOngoingSync(id, siteId);
     }
 
     /**
@@ -331,10 +323,10 @@ export class CoreSyncBaseProvider<T = void> {
      */
     protected get componentTranslate(): string {
         if (!this.componentTranslateInternal) {
-            this.componentTranslateInternal = Translate.instant(this.componentTranslatableString);
+            this.componentTranslateInternal = <string> Translate.instant(this.componentTranslatableString);
         }
 
-        return this.componentTranslateInternal!;
+        return this.componentTranslateInternal;
     }
 
 }
diff --git a/src/core/classes/site.ts b/src/core/classes/site.ts
index ea5786eca..5dac39fee 100644
--- a/src/core/classes/site.ts
+++ b/src/core/classes/site.ts
@@ -591,8 +591,7 @@ export class CoreSite {
 
                 return response;
             } catch (error) {
-                if (error.errorcode == 'invalidtoken' ||
-                    (error.errorcode == 'accessexception' && error.message.indexOf('Invalid token - token expired') > -1)) {
+                if (CoreUtils.isExpiredTokenError(error)) {
                     if (initialToken !== this.token && !retrying) {
                         // Token has changed, retry with the new token.
                         preSets.getFromCache = false; // Don't check cache now. Also, it will skip ongoingRequests.
diff --git a/src/core/features/comments/services/comments-sync.ts b/src/core/features/comments/services/comments-sync.ts
index 1055c8c4b..f402366f8 100644
--- a/src/core/features/comments/services/comments-sync.ts
+++ b/src/core/features/comments/services/comments-sync.ts
@@ -158,10 +158,11 @@ export class CoreCommentsSyncProvider extends CoreSyncBaseProvider<CoreCommentsS
         siteId = siteId || CoreSites.getCurrentSiteId();
 
         const syncId = this.getSyncId(contextLevel, instanceId, component, itemId, area);
+        const currentSyncPromise = this.getOngoingSync(syncId, siteId);
 
-        if (this.isSyncing(syncId, siteId)) {
+        if (currentSyncPromise) {
             // There's already a sync ongoing for comments, return the promise.
-            return this.getOngoingSync(syncId, siteId)!;
+            return currentSyncPromise;
         }
 
         this.logger.debug('Try to sync comments ' + syncId + ' in site ' + siteId);
diff --git a/src/core/features/course/services/sync.ts b/src/core/features/course/services/sync.ts
index 3516f578d..3b29dc151 100644
--- a/src/core/features/course/services/sync.ts
+++ b/src/core/features/course/services/sync.ts
@@ -117,9 +117,10 @@ export class CoreCourseSyncProvider extends CoreSyncBaseProvider<CoreCourseSyncR
     async syncCourse(courseId: number, siteId?: string): Promise<CoreCourseSyncResult> {
         siteId = siteId || CoreSites.getCurrentSiteId();
 
-        if (this.isSyncing(courseId, siteId)) {
+        const currentSyncPromise = this.getOngoingSync(courseId, siteId);
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this discussion, return the promise.
-            return this.getOngoingSync(courseId, siteId)!;
+            return currentSyncPromise;
         }
 
         this.logger.debug(`Try to sync course '${courseId}'`);
diff --git a/src/core/features/pushnotifications/services/pushnotifications.ts b/src/core/features/pushnotifications/services/pushnotifications.ts
index ba07fa9d3..a4aadf0a7 100644
--- a/src/core/features/pushnotifications/services/pushnotifications.ts
+++ b/src/core/features/pushnotifications/services/pushnotifications.ts
@@ -524,7 +524,13 @@ export class CorePushNotificationsProvider {
         try {
             response = await site.write<CoreUserRemoveUserDeviceWSResponse>('core_user_remove_user_device', data);
         } catch (error) {
-            if (CoreUtils.isWebServiceError(error)) {
+            if (CoreUtils.isWebServiceError(error) || CoreUtils.isExpiredTokenError(error)) {
+                // Cannot unregister. Don't try again.
+                await CoreUtils.ignoreErrors(db.deleteRecords(PENDING_UNREGISTER_TABLE_NAME, {
+                    token: site.getToken(),
+                    siteid: site.getId(),
+                }));
+
                 throw error;
             }
 
diff --git a/src/core/features/rating/services/rating-sync.ts b/src/core/features/rating/services/rating-sync.ts
index 9e6027ca9..09f1af9c2 100644
--- a/src/core/features/rating/services/rating-sync.ts
+++ b/src/core/features/rating/services/rating-sync.ts
@@ -157,9 +157,10 @@ export class CoreRatingSyncProvider extends CoreSyncBaseProvider<CoreRatingSyncI
         siteId = siteId || CoreSites.getCurrentSiteId();
 
         const syncId = this.getItemSetSyncId(component, ratingArea, contextLevel, instanceId, itemSetId);
-        if (this.isSyncing(syncId, siteId)) {
+        const currentSyncPromise = this.getOngoingSync(syncId, siteId);
+        if (currentSyncPromise) {
             // There's already a sync ongoing for this item set, return the promise.
-            return this.getOngoingSync(syncId, siteId)!;
+            return currentSyncPromise;
         }
 
         this.logger.debug(`Try to sync ratings of component '${component}' rating area '${ratingArea}'` +
diff --git a/src/core/features/user/services/user-sync.ts b/src/core/features/user/services/user-sync.ts
index 7f5eca734..a09fd892c 100644
--- a/src/core/features/user/services/user-sync.ts
+++ b/src/core/features/user/services/user-sync.ts
@@ -54,10 +54,11 @@ export class CoreUserSyncProvider extends CoreSyncBaseProvider<string[]> {
         siteId = siteId || CoreSites.getCurrentSiteId();
 
         const syncId = 'preferences';
+        const currentSyncPromise = this.getOngoingSync(syncId, siteId);
 
-        if (this.isSyncing(syncId, siteId)) {
+        if (currentSyncPromise) {
             // There's already a sync ongoing, return the promise.
-            return this.getOngoingSync(syncId, siteId)!;
+            return currentSyncPromise;
         }
 
         this.logger.debug('Try to sync user preferences');
diff --git a/src/core/lang.json b/src/core/lang.json
index 08efb25f7..99182daa6 100644
--- a/src/core/lang.json
+++ b/src/core/lang.json
@@ -60,6 +60,7 @@
     "coursedetails": "Course details",
     "coursenogroups": "You are not a member of any group of this course.",
     "currentdevice": "Current device",
+    "custom": "Custom",
     "datastoredoffline": "Data stored in the device because it couldn't be sent. It will be sent automatically later.",
     "date": "Date",
     "day": "day",
@@ -157,6 +158,8 @@
     "maxsizeandattachments": "Maximum file size: {{$a.size}}, maximum number of files: {{$a.attachments}}",
     "min": "min",
     "mins": "mins",
+    "minute": "minute",
+    "minutes": "minutes",
     "misc": "Miscellaneous",
     "mod_assign": "Assignment",
     "mod_assignment": "Assignment 2.2 (Disabled)",
@@ -330,6 +333,8 @@
     "viewprofile": "View profile",
     "warningofflinedatadeleted": "Offline data from {{component}} '{{name}}' has been deleted. {{error}}",
     "warnopeninbrowser": "<p>You are about to leave the app to open the following URL in your device's browser. Do you want to continue?</p>\n<p><b>{{url}}</b></p>",
+    "week": "week",
+    "weeks": "weeks",
     "whatisyourage": "What is your age?",
     "wheredoyoulive": "In which country do you live?",
     "whoissiteadmin": "\"Site Administrators\" are the people who manage the Moodle at your school/university/company or learning organisation. If you don't know how to contact them, please contact your teachers/trainers.",
diff --git a/src/core/services/local-notifications.ts b/src/core/services/local-notifications.ts
index c6547f8fe..9b69435e0 100644
--- a/src/core/services/local-notifications.ts
+++ b/src/core/services/local-notifications.ts
@@ -653,9 +653,19 @@ export class CoreLocalNotificationsProvider {
      */
     async trigger(notification: ILocalNotification): Promise<number> {
         const db = await this.appDB;
+        let time = Date.now();
+        if (notification.trigger?.at) {
+            // The type says "at" is a Date, but in Android we can receive timestamps instead.
+            if (typeof notification.trigger.at === 'number') {
+                time = <number> notification.trigger.at;
+            } else {
+                time = notification.trigger.at.getTime();
+            }
+        }
+
         const entry = {
             id: notification.id,
-            at: notification.trigger && notification.trigger.at ? notification.trigger.at.getTime() : Date.now(),
+            at: time,
         };
 
         return db.insertRecord(TRIGGERED_TABLE_NAME, entry);
diff --git a/src/core/services/utils/utils.ts b/src/core/services/utils/utils.ts
index 6d06cbf3d..938a48778 100644
--- a/src/core/services/utils/utils.ts
+++ b/src/core/services/utils/utils.ts
@@ -850,7 +850,7 @@ export class CoreUtilsProvider {
     }
 
     /**
-     * Given an error returned by a WS call, check if the error is generated by the app or it has been returned by the WebSwervice.
+     * Given an error returned by a WS call, check if the error is generated by the app or it has been returned by the WebService.
      *
      * @param error Error to check.
      * @return Whether the error was returned by the WebService.
@@ -858,10 +858,22 @@ export class CoreUtilsProvider {
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     isWebServiceError(error: any): boolean {
         return error && (typeof error.warningcode != 'undefined' || (typeof error.errorcode != 'undefined' &&
-                error.errorcode != 'invalidtoken' && error.errorcode != 'userdeleted' && error.errorcode != 'upgraderunning' &&
+                error.errorcode != 'userdeleted' && error.errorcode != 'upgraderunning' &&
                 error.errorcode != 'forcepasswordchangenotice' && error.errorcode != 'usernotfullysetup' &&
                 error.errorcode != 'sitepolicynotagreed' && error.errorcode != 'sitemaintenance' &&
-                (error.errorcode != 'accessexception' || error.message.indexOf('Invalid token - token expired') == -1)));
+                !this.isExpiredTokenError(error)));
+    }
+
+    /**
+     * Given an error returned by a WS call, check if the error is a token expired error.
+     *
+     * @param error Error to check.
+     * @return Whether the error is a token expired error.
+     */
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    isExpiredTokenError(error: any): boolean {
+        return error.errorcode === 'invalidtoken' ||
+            (error.errorcode === 'accessexception' && error.message.includes('Invalid token - token expired'));
     }
 
     /**