First you can open your calendar and click on the “Event Lists” tab to open the event lists.
Check the box next to each event you want to remove, go to the top and click the delete button.

Now, while still in Calendar, click on “Options” in the upper right.
Click on “Time Guides.”
Uncheck the “Groups.”
Save
If you don’t find it there, click on “Sharing.”
Click on “My Friends.” [Edit List]
Delete the offender.
Save