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 and click Delete or Unsubscribe Calendar on the Calendar toolbar on the left pane.