Hello @hbrown5018
Thanks for posting this in the Global Canvas Community.
The only way I know of is to do this one by one. Unfortunately, I did not see that there is not a bulk edit option for Calendar items.
One work around I have found is to pull up the syllabus page and look at the Course Summary. The course summary should show any assignments, quizzes, discussions, and events that are set up in the course. When you click on the item, it should take you to the area where the item is setup and you can delete any unwanted items.
This might be a little off topic, but If they are seeing assignments, quizzes, and discussions with old 2020 dates, there is a way to bulk edit the due dates. This comes in handy if they plan on using some of the content, but wish to reconfigure the dates for their current year. HERE is a guide on how to do that.
It does sound like the items are being imported from the old course from 2020. One way I have found to avoid this is to select the Adjust Events and Due Dates option before they do the import. They can either choose the option to Shift Dates, or Remove Dates. HERE is the Canvas guide that goes over that information.
Hopefully this helps!
-Colton