Best Calendar apps?

Hey!

I am trying to switch away from my Samsung Calendar (not because of Samsung as much as because I can practically only synch it with the Google Calendar).

Any recommendations?

I am working now with Tuta Calendar, but it lacks some features. For example, I cannot customize the time of the reminder (there are only five options to choose from). Also, it is not too easy to copy the events, which makes putting the same things manually every week sluggish.

Or maybe somebody knows how to tweak Samsung calendar to accept calendar synch with an open-source protocol?