Calendar keep removing birthdays when I quit and reopen

Hello Lundrim24.

Thanks for the clarification. Start by doing a safe boot of the Mac. This will clear some system caches and give you a good foundation moving forward.

Use safe mode to isolate issues with your Mac - Apple Support

If you safe boot the Mac, then reboot normally and the issue persists, set up a new admin account for testing.

How to test an issue in another user account on your Mac - Apple Support

Cheers.

Hello Lundrim24 and welcome to Apple Support Communities.

I see you're having an issue with the birthday information appearing consistently in your Calendar app.

Birthday info would normally be stored in the Contacts app and not in the Calendar app. Are you referring to info that has been added to individual contacts or are you referring to birthday info that's connected to the Calendar app via a third-party service such as Facebook?

If this data is coming via a subscription, what happens when you open the Contacts app and add the birthday info manually?

Cheers.

Hi Lundrim24.

Glad to hear that got you sorted. Have a brilliant rest of your day!

Cheers.