Refactor all-day events logic

src/widgets/calendar/integrations/ical.jsx

@@ -52,12 +52,10 @@ export default function Integration({ config, params, setEvents, hideErrors, tim
       }
 
       const eventToAdd = (date, i, type) => {
-        // When the 'dtend' is not defined (one-day all-day event), 'dtend' should be the same as 'dtstart'.
-        const { dtstart } = event;
-        const dtend = 'dtend' in event ? event.dtend : dtstart;
+        // 'dtend' is null for all-day events
+        const { dtstart, dtend = { value: 0 } } = event;
 
-        const duration = dtend.value - dtstart.value;
-        const days = duration === 0 ? 1 : duration / (1000 * 60 * 60 * 24);
+        const days = dtend.value === 0 ? 1 : (dtend.value - dtstart.value) / (1000 * 60 * 60 * 24);
 
         const eventDate = timezone ? DateTime.fromJSDate(date, { zone: timezone }) : DateTime.fromJSDate(date);