I have a faculty member who has asked this question and provided the following information:

I have assignments from 2020 that keep popping up on my calendar and to-do list. There are enough of these that I need a quick way to get rid of the outdated entries (without having to remove them one-by-one).

My thought is they've done several course copies and have not deleted any old assignments or to-do's from the previous course copies? 

Thank you for your assistance! Heather