Id like to cleanup the calendars references to past assignments. How do I do that?
DO NOT DELETE an automatically-added calendar reference in the calendar maintenance page! Presently, this WILL REMOVE the event, the assignment/quiz/etc. itself, and any associated grades! INSTEAD, just make the assigment/quiz/etc. invisible and the calendar reference will disappear too. If you MANUALLY added a calendar event, then you would use the calendar’s X icon to delete it. This difference in behaviour is confusing, and has been reported to moodle.org for their consideration.