Hello Arnold, others,
I'm a Program Manager on the Mac Outlook team. Thanks for reporting the issues here and on Mac Outlook forum.
We are aware of the Calendar day/date header issue. Can you please confirm if the following repro mitigates the issue - 1. Switch away from Calendar to Mail or People or Tasks or Notes
2. Quit Outlook
3. Re-launch Outlook and switch to Calendar module
Thanks for your feedback and apologies for the inconvenience.
Sunder