apps/api/src/broker/expand.ts

@@ -209,8 +209,13 @@ export function expandOccurrences(
   const allDay: boolean = dtstart.isDate
   const uid: string = event.uid ?? ''
 
-  const rangeStart = ICAL.Time.fromJSDate(windowStart, false)
-  const rangeEnd = ICAL.Time.fromJSDate(windowEnd, false)
+  // useUTC=true: windowStart/windowEnd are absolute instants (midnight-UTC of the
+  // requested dates). Interpreting them in UTC keeps the occurrence-window comparison
+  // absolute. With useUTC=false ical.js used the SERVER's local timezone, shifting the
+  // window by the server's offset and dropping evening occurrences near the window end
+  // (e.g. a 17:45-04:00 event = 21:45Z fell past a day window whose end was shifted to 20:00).
+  const rangeStart = ICAL.Time.fromJSDate(windowStart, true)
+  const rangeEnd = ICAL.Time.fromJSDate(windowEnd, true)
 
   const occurrences: CalendarOccurrence[] = []