Go to Calendar > Edit Calendars > Edit if you want to adjust the hours that shows on the calendar inside Appointment Reminder.
Once you have set these hours you can then adjust to further settings if you wish.
Only sync appointments between start and end hours. Helpful when add non actual appointments outside of normal appointments. For example you keep a waitlist.
If you go to Settings > Business Settings you can enable "Only Send Reminders during Calendar Hours"
