In my calendar app u have an unwanted calendar. When I try to delete it there is no delete option. Why?

A delete button would indeed be very helpful. The calendar "Help" menu suggests you delete a specific calendar through the "edit" menu. However, that is not working for most of my calenders.

Here is a copy from from the "help":

Delete a calendar

1. In the Calendar app on your Mac, click the calendar’s name in the calendar list.
2. If you don’t see the calendar list on the left, choose View > Show Calendar List.
3. Choose Edit > Delete.
4. Some calendars can’t be deleted.

• • You can’t delete delegated calendars, but you can stop showing them in the main Calendar window. See Share calendar accounts.
  • If you can’t delete a calendar for a particular calendar account, try deleting the calendar on the account provider’s website. For example, to delete a Google calendar, go to google.com.
  • If a calendar account has only one calendar (not counting other people’s calendars you’re sharing), you can’t delete that last calendar.