- Add formatDateTimeInTimezone() helper to format dates in event's original timezone
- Fix EventUpdateModal to display event times in original timezone instead of browser timezone
- Fix EventModal (duplicate event) with same timezone handling
- Update EventDisplay tests to use flexible date pattern
- Add byday field to RepetitionObject interface in EventsTypes.ts
- Update calendarEventToJCal to handle byday field (array or null)
- Update parseCalendarEvent to parse byday from JCal format
- Fix all-day event dtend logic to increment by 1 day when start equals end
- Add comprehensive test cases for byday field handling