To unsubscribe from a calendar perform the following steps:
Right-click the calendar to unsubscribe.
The following options appear:
Properties
Unsubscribe
Select Unsubscribe.
The Remove Subscribed Calendar dialog appears.
Click OK to unsubscribe from the calendar.
Optionally, you can select the calendar:
Click the Delete or Unsubscribe Calendar icon on the Calendar toolbar in the left pane in two-pane layout.
Click Delete or Unsubscribe Calendar from the Actions drop-down list on the Calendar toolbar in the left pane in three-pane layout.