Canceling an appointment will remove it from your calendar.
From the Calendar view, tap on the 'Appointments' button to view your appointments for the selected date:
From this screen, select the appointment you wish to cancel.
Doing this will open the appointment details screen:
Once on this screen, tap on the 'Cancel' button. You will be prompted whether you are sure you want to cancel the appointment:
When you tap 'Yes' the appointment will be canceled and removed from your calendar. You will then be taken back to the Calendar View.