On a calendar view, click and hold the appointment you wish to adjust and drag it to when you want it rescheduled.

A box will pop up, just like in the picture below.

You may opt to "Automatically recalculate the amount owed for the said appointment" if you charge hourly by checking the box below.

On recurring appointments, you can also choose whether to apply the changes only for this specific appointment or change all future appointments by selecting one of the options shown below.

When done, click “Save”.