Calendear

If I were to (as the story goes) get a job at Google, fix one bug, and quit, this is the bug I would fix: the same event should only be shown on your Calendar once, even if you can see the event on multiple calendars.

Google Calendar

Calendear shows this sensibly

Calendear also lets you paste an image to add a calendar entry. The models that Apple Intelligence ships are good enough to OCR the image and parse some dates out, so this can be done locally.

I went through the motions, and it's out in the App Store. Not in Europe. The price can't be beat.