I'm a complete idiot, and totally failed to test the iCal import functionality
with iCalcreator v2.22. Turns out, the author made much more significant changes
to the library than I'd thought, and those changes completely broke the import
process. With several hours of work, I could probably re-write Date iCal to
support these changes, but those re-writes would necessarily make Date iCal
incompatible with v2.20.2 of the library, which would break every existing Date
iCal install the next time they update, unless they also update iCalcreator.

Thus, due to my lack of available time, and the update incompatibility problem,
I'm just declaring that Date iCal 7.x will not support iCalcreator v2.22, ever.
If someone comes along to make a Drupal 8 version, they could choose to put in
the time to re-write the guts of the import code to make it v2.22-compatible.