Office 365 (Outlook Client for for Windows) - Delete a Shared Calendar
Any calendar you’ve created in Outlook can be deleted except the primary Outlook calendar, which is used to keep track of meeting requests that you send and accept as well as appointments and events you schedule. Additional calendars that you open, such as shared or team calendars may be deleted and removed from the folder pane and the Calendar.
1. Right-click the calendar in the folder pane on the left and then click Delete Calendar.
Outlook asks you if you want to remove the group calendar and move its contents into the Deleted Items folder.
2. Click Yes to confirm the deletion.