I just wanted to see if anyone had some solutions to my problems. I'm trying to use Calendar, but when I add an "On the Web" calendar, it just doesn't work. So, I added my calendar through Evolution instead (since it connects to Calendar somehow), which works perfectly. However, when I returned to Calendar, some of my events showed up, and others did not. And, events were out of order and duplicated. I guess I can just use Evolution, but I'd much rather use Calendar, since it just looks so much better. I have updated my elementary OS to version 5.1. I hope this is enough information! If you need clarification, just tell me.
I find a solution of my daily usage for Caldav, I hope they work with web calendar... (But if you see in calendar there is not "web calendar" but just "Caldav"...) I add Caldav first in calendar, then,I change Caldav properties in evolution to save Caldav identifiers in calendar and evolution (in order to add event in evolution or calendar). I go to evolution and change the calendar update in calendar propreties. Chose the shortest time (1 minute). The cool thing is that can work even when evolution is not launch (at start-up for example). For example when i add an event in calendar, the event is visible quickly in calendar according to the update cycle of one minute. Actually, when the set up is complete, I never use evolution except to manage online contact. In addition, I think there is a conflict between evolution and calendar for certain events. Clear problematic events (directly in your online service), restart your computer and re-record events with calendar. I hope that calendar can be autonomous in the futur with evolution data-server or something like that.