If you suspect your calendar is on iCloud, you can login to your account at www.icloud.com.
Click on the Calendar section of the link below from the iCloud help site.
Delete a calendar
When you delete a calendar from your Calendars list, all events associated with the calendar are also deleted.
You can’t delete all of the calendars in the list because the list must always must contain at least one calendar.
WARNING: Any calendar deletions you make appear on every device where you turned on iCloud Calendar. For example, if you have iCloud Calendar turned on on your iPhone and your Mac, when you delete a calendar from iCloud Calendar on the web, the calendar is also deleted from the Calendar app on your iPhone.
- Click Edit in the sidebar.
- Click the Delete button to the right of the calendar’s name.
- Click Delete Calendar.If the calendar is shared, a window appears asking whether or not to send a notification email to calendar participants. If you choose not to notify participants via email, they’re notified the next time they sign in to iCloud that the calendar is no longer available.
I hope this information helps ....
Have a great day!