Single calendar api to work with google/apple/outlook? Or need separate code/packages for each?

I see a couple of services like that let you use one api for a bunch of calendars, are there any open source options? Has anyone had to tackle this in the past? I suppose regardless of cronofy or not, you have to setup oauth flows for each?

Would CalDAV be of use?

Googled it, and I think maybe. It doesn’t seem very popular though. I wonder why

I’ve been using Cronofy with my SaaS app Focuster. It works pretty well though it doesn’t give you low-level access to the underlying calendar backend. but that’s probably fine for 80% of applications. Basically, they present a unified view across all the calendar services. I’ve spoken with their CEO and support team and they’ve been responsive and helpful.