The Calendars app in macOS Catalina is automatically backed up if you have an iCloud account and enable this option. However, I like to keep another back-up of my calendar events and urge you to do the same.
Here’s how to make a backup of your Mac’s Calendar:
- Launch Calendar.
- From the Calendar sidebar, choose the calendar you want to back up.
- From the menus, select File > Export.
- Use the Save dialog box to browse to a location on your Mac to store the backup, click the Export button.
The selected calendar will be saved in iCal (.ics) format. Repeat for any other calendars you wish to back up. Saving these files on an external drive is also recommended in case you have problems with your computer.