Disable the Contact Time Zone
If disabled, appointment reminders will not work properly, and the contact will not be able to change them. Time zones (Location vs. Prospect).
There will be a time zone based on the prospect's time zone and a time zone based on the location's time zone in the appointment reminders.
As an Example:
East coast company books appointment with west coast company. Location (Westcoast) gets appointment at 2pm, while east gets appointment at 5pm.