How do I get Caldav to work with iCloud calendar?

Have you read the How-To provided by Apple? I got an ICloud calendar which synchs just fine. Unfortunately i set it up over 9 months ago and I don't remember how exactly I have done it. I just know that the above mentioned How-To helped me out after many attempts with no success.

Can you provide a link to this How-to?

I have two separate calendar endpoints for CalDAV, and I've noticed that I had to close the calendar app, delete the calendar database, sync both calendar accounts (via account settings) and finally open the calendar app again. Only after that the app accepted the second calendar source. Before this I could see other calendar flashing in during sync. If you see this, you could try the same.

Calendar database files can be found under /home/nemo/.local/share/system/privileged/Calendar/. You need to do rm command as devel-su.

Regarding your original question, I don't have iCloud to test with, but Zimbra server uses the same method (known urls) to sync with iPhone, and there "it just works". So there shouldn't be anything special to configure and it should find your paths automatically (and it does during the creation of account so it should work). That's why I suspect the problem might be in calendar database itself.

Thanks for the advice. I had already tried deleting the calendar databases after having deleted the iCloud/Caldav account and then adding the account again. That did not help. Now I've also tried deleting the database without removing the account first, and then just syncing the account after deleting the database. But unfortunately no luck...

It's a bit strange why it doesn't work, because I can sync to another Caldav account. And my colleagues have successfully synced their Blackberry phones to the iCloud calendar with exactly the same information, i.e. https://caldav.icloud.com and Apple ID.