When you register an account on Appointment Reminder all reminders will be sent 24 hours before the time of the Appointment.
If you wish to change this, follow these instructions.
Login to Appointment Reminder
Click Settings > Business Settings
You will see an option that says "How many hours before appointment we should we send the reminder (default 24 hours)".
Change this to your desired time.
If you want to MULTIPLE REMINDERS for each appointment then you will want to use Sequences.
Note: You can also change the default send time for each specific calendar. To do this
Go to Settings > Edit Calendars
Click edit on the calendar you want to edit.
Right down the bottom of the page you will see an option that says "How many hours before appointment we should we send the reminder (default 24 hours)".
Change this to your desired time.
If you want your reminders to go at a specific time for example 1pm the day before the appointment then choose the "Custom" option. In the days before enter 1. If you wanted the reminder to go 7 days before you would enter 7.
Note you can also change each individual appointment when creating them in the Appointment Reminder calendar or in Outlook Calendar. Setting the default send time is a great way to speed up the process of entering appointments.
Please note updating the send time doesn't affect the existing appointments in the calendar. If you are wanting to update the existing appointments you should run a full sync on the calendar.