As of macOS 13 (Ventura), there have been changes whereby the previous method no longer works and an error occurs ("Account name/password could not be verified.").
The following two options via Exchange (recommended) or Caldav now exist, but may not work reliably.
The personal mailbox including calendar must be added as an account via Exchange. -> Instructions for mailbox integration
Switch to Accounts > Server settings .
Here the server path must be changed to the calendar to be subscribed to. In the example: /principals/users/berta.musterfrau@uni-bielefeld.de/
Close settings.
The subscribed calendar is now displayed and no longer the personal calendar. If the personal calendar is to be displayed again, steps 1-3 must be repeated.
Account type:
-> Advanced
Username:
-> Email (for which the authorisation exists)
Password:
-> BITS password
Server address:
-> caldav.uni-bielefeld.de
Server path:
-> /principals/users/Uni-E-Mail-Adresse@uni-bielefeld.de/
Example:
/principals/users/berta.musterfrau@uni-bielefeld.de/
Port:
-> 443
Finally, click on Registration .