If the AllDay property equals true, the appointment lasts for one or multiple days. The exact time of both Start and End dates are ignored. If the End day's time is not equal 0:00, this day is included in the event.
Otherwise, if the End day's time equals 0:00, the event lasts until 23:59:59 of the day before and does not include this End day.
When users create or modify appointments at runtime using the Appointment Edit Form, the End is also included in the event duration.
All-day appointments do not belong to any time zone. When the current time zone of the scheduler (obtained from the host settings or specified by the SchedulerOptionsBehaviorBase.ClientTimeZoneId property) changes, the Start and End properties of the all-day appointment remain the same.