How to set up Calendars in iCal
- Run the Apple iCal/Calendar application

- In the menu, select iCal/Calendar → Preferences

- go to tab Accounts
- Click on the + button to create a new account

- Choose Add CalDav Account...

- Choose Account Type: Manual
- Type your User Name, Password and Server Address [domain.tld]

- Next step you need Verify Certificate
- Choose Show Certificate

- Choose Trust

- Choose Always trust
