AppointmentItem.EndTimeZone Property (Outlook)
Returns or sets a TimeZone value that corresponds to the end time of the appointment. Read/write.
The time zone information is used to map the appointment to the correct UTC time when the appointment is saved, and into the correct local time when the item is displayed in the calendar.
Depending on the circumstances, changing the EndTimeZone may or may not cause Outlook to recalculate and update the AppointmentItem.EndInEndTimeZone.
As an example, in the appointment inspector, if you are the organizer of an appointment with a start time at 1 P.M. EST and end time at 3 P.M. EST, changing the appointment to have an EndTimeZone of PST will result in an appointment lasting from 1 P.M. EST to 3 P.M. PST, with the EndInEndTimeZone remaining as 3 P.M. However, if you are not the organizer, then changing the EndTimeZone from EST to PST will cause Outlook to recalculate and update the EndInEndTimeZone, and the appointment will last from 1 P.M. EST to 12 P.M. PST.
Another example is changing the EndTimeZone resulting in an appointment end time that occurs before a previously set appointment start time, in which case Outlook will recalculate and update the EndInEndTimeZone. For example, an appointment with a start time at 1 P.M. PST and end time at 3 P.M. PST has its EndTimeZone changed to EST. If Outlook did not recalculate the EndInEndTimeZone, the appointment would have an end time at 3 P.M. EST, which is equivalent to 12 P.M. PST, and which would occur before the start time of 1 P.M. PST. In practice, however, changing the EndTimeZone would result in Outlook recalculating and updating the EndInEndTimeZone to 6 P.M. (in the EndTimeZone EST).