Fix time shift when editing custom events

aleksis/core/frontend/components/calendar_feeds/details/CustomDetails.vue

@@ -84,8 +84,8 @@ export default {
         title: this.selectedEvent.name,
         description: this.selectedEvent.meta.description,
         location: this.selectedEvent.location,
-        datetimeStart: this.selectedEvent.start,
-        datetimeEnd: this.selectedEvent.end,
+        datetimeStart: this.selectedEvent.startDateTime.toISO(),
+        datetimeEnd: this.selectedEvent.endDateTime.toISO(),
       };
     },
   },