During testing, we found an issue that occurs with non-synced calendars. When crossing timezones, an all-day event can spill over into another day (either forward or backward, depending on which way you are traveling), making it a 2-day all-day event.
This led to quite a bit of confusion during testing, so we decided to remove the option to export your schedule to non-synced (local-only) calendars.
This shouldn't affect most people, as the main reason for exporting is to share their schedule with others, or put their schedule on a family calendar.
If you still have questions, please send us an email to firstname.lastname@example.org