How does your app manage external calendar events?

I want to write events to a calendar, keep them up to date and perhaps cancel them on reasonably short notice. While supporting any calendar app (not just Google Calendar).

How have you solved this in the past (or present)? Is there a service/project that handles this smoothly?

My gut tells me that this problem has been solved many, many times before, and that someone may have written a service for it, but I can't seem to find anything.

The obvious choice seems to be the open formats: CalDAV, iCalendar etc. But I read nothing but bad things about integration with the likes of Google Calendar. From data loss to 12-24 hour delays in syncing.

So that pushes me to API integration. But integrating with every calendar API out there seems like a never-ending job.

Any insights and help are welcome.

GCal data loss: https://evertpot.com/google-carddav-issues/

GCal delays: https://help.cheqroom.com/en/articles/1502123-why-is-my-google-calendar-sync-slow-or-not-updating-at-all