Calender crashing Big Sur

Hi JustCalv,

We understand you're not able to open the Calendar app. Are you using the built in Calendar app or a third-party app? To isolate further, are you able to open it in another user account? Being able to see if the issue occurs in another user account will help us to identify if it is something that is affecting your entire system or just one particular user account. To do this, we will want to set up a Test User account and then try to replicate the issue in that account.

1. Choose Apple menu  > System Preferences, then click Users & Groups.

2. Click the lock lock icon, then enter an administrator name and password.

3. Click the add button (+) below the list of users.

4. Complete the fields shown for a Standard or Administrator account, then click Create Account (or OK).

5. Go back up to the Apple menu  in the upper left of the computer and select "Log Out". At the login screen, choose the "Test User" we just made.

6. Once inside the Test Account, try to replicate the issue so we can determine if it just occurs in one account or on the whole computer.

Hope this helps!

Have a great day.