Set initial calendar event date based on active calendar view (#14516)

src/panels/calendar/dialog-calendar-event-editor.ts

@@ -73,7 +73,11 @@ class DialogCalendarEventEditor extends LitElement {
       }
     } else {
       this._allDay = false;
-      this._dtstart = startOfHour(new Date());
+      // If we have been provided a selected date (e.g. based on the currently displayed
+      // day in a calendar view), use that as the starting value.
+      this._dtstart = startOfHour(
+        params.selectedDate ? params.selectedDate : new Date()
+      );
       this._dtend = addHours(this._dtstart, 1);
     }
   }

src/panels/calendar/ha-full-calendar.ts

@@ -276,8 +276,19 @@ export class HAFullCalendar extends LitElement {
   }
 
   private _createEvent(_info) {
+    // Logic for selectedDate: In week and day view, use the start of the week or the selected day.
+    // If we are in month view, we only use the start of the month, if we are not showing the
+    // current actual month, as for that one the current day is automatically highlighted and
+    // defaulting to a different day in the event creation dialog would be weird.
     showCalendarEventEditDialog(this, {
       calendars: this._mutableCalendars,
+      selectedDate:
+        this._activeView === "dayGridWeek" ||
+        this._activeView === "dayGridDay" ||
+        (this._activeView === "dayGridMonth" &&
+          this.calendar!.view.currentStart.getMonth() !== new Date().getMonth())
+          ? this.calendar!.view.currentStart
+          : undefined,
       updated: () => {
         this._fireViewChanged();
       },

src/panels/calendar/show-dialog-calendar-event-detail.ts

@@ -2,7 +2,7 @@ import { fireEvent } from "../../common/dom/fire_event";
 import { Calendar, CalendarEventData } from "../../data/calendar";
 
 export interface CalendarEventDetailDialogParams {
-  calendars: Calendar[]; // When creating new events, is the list of events that support creation
+  calendars: Calendar[]; // When creating new events, is the list of calendar entities that support creation
   calendarId?: string;
   entry?: CalendarEventData;
   canDelete?: boolean;

src/panels/calendar/show-dialog-calendar-event-editor.ts

@@ -2,8 +2,9 @@ import { fireEvent } from "../../common/dom/fire_event";
 import { Calendar, CalendarEventData } from "../../data/calendar";
 
 export interface CalendarEventEditDialogParams {
-  calendars: Calendar[]; // When creating new events, is the list of events that support creation
+  calendars: Calendar[]; // When creating new events, is the list of calendar entities that support creation
   calendarId?: string;
+  selectedDate?: Date; // When provided is used as the pre-filled date for the event creation dialog
   entry?: CalendarEventData;
   canDelete?: boolean;
   updated: () => void;