Article from Maemo.Org:
so after a month long struggle, I finally managed to synchronise my CalDAV calendars with the N9 and my Mac. I'll write it down here, in case this helps anyone else.
IN YOUR MAC:
1) Setup the basic free iCloud access to store your calendars and contacts.
2) Discover which is your iCloud CalDAV URL. To do so, open the Terminal in your Mac, and go to your calendars directory:
3) Find out which file contains your main calendar; if you sync some calendars with Google, like I do, you might have several configurations. Try the following:
grep -r "PrincipalURL" *
This will return one or more filenames, similar to:
4) Check each of the files the previous command returned, with a text editor, for the line saying "PrincipalURL"; one of them will have an iCloud URL in the following line, similar to "https://p-02-caldav.icloud.com:443/9999999999/principal".
IN YOUR N9:
1) Go to "Accounts", then "Add accounts", then "CalDAV Calendar";
2) Your username and password are your iCloud access codes (usually your Apple ID and password), and the Server/URL is the "PrincipalURL" of your calendar.
That's it, it syncs beautifully. Now I only have to figure out how to sync contacts (I found the iCloud URL for them, but the N9 doesn't want to sync contacts through CalDAV, anyone got an idea?).