Overlapping events in Calendar.app

Hello there, preske,

Typically, multiple events occurring simultaneously would display with a slight overlap, if one starts just before another is ending, or side-by-side if they begin or end at the same time. Take a look at the information outlined in Calendar User Guide for Mac - Apple Support for more information.

Since yours appear to be overlapping unexpectedly outside of those parameters, we have some troubleshooting steps we can advise which will help isolate and potentially resolve the issue. We suggest doing the steps in order, testing between each:

1. Quit the Calendar app: Quit apps on Mac - Apple Support and reopen it while holding shift
2. Restart your Mac: Shut down or restart your Mac - Apple Support
3. See if you can replicate the issue in safe mode: How to use safe mode on your Mac - Apple Support
4. See if the issue continues in a new user account: Set up users, guests, and groups on Mac - Apple Support

Best.