How to identify which projects are using calendars

This is a similar issue to when trying to clean up the resource library. Where is it seems to be nearly impossible for Oracle to provide a solution. (Hopefully this is not the case for calendars)

When deleting "trash" calendars (from imports, test projects, practice etc) more often than not you get the error that you can't delete the calendar because it's being used by an activity.

The error does not identify which activity or which project making it impossible to delete the calendar.

Is there anyway to identify which projects are using certain calendars?