You can create or delete calendars. When you delete a calendar, you also delete all events in the calendar and decline any invitations you've received in the calendar. You can't undo deleting a calendar so be careful.
To create a calendar:
While viewing a personal or group calendar, click the Create Calendar (+) button.
Enter a name for the calendar in the Calendar Name field.
To change the calendar's color, choose a different color from the Calendar Color pop-up menu.
To delete a calendar:
While viewing a personal or group calendar, hold the mouse cursor over the calendar you want to delete and then click the Information (i) button.
If you have only one calendar, you can't delete it.
Click Delete and then click OK.