This was resolved in Build 6948 (Jan 9, 2019) Fixed: Creating appointments in web interface with a specified time zone other than the one the server is set adjusts incorrectly the start/end times. Unfortunately, old appts would have already been written to the system with the incorrect dates/times. This will not be a retroactive fix but should prevent the issue on future appointments.
Andrea Free
SmarterTools Inc.
877-357-6278
www.smartertools.com