If you have issues on your Mac, one thing you don’t want to lose is your calendars. If your calendars are set to back up to iCloud, it still is a good idea to make a physical backup of your calendars on your Mac occasionally. This article describes how to create a calendar backup on your Mac. I have used the BusyCal App for years which has its own backup feature. I am sure Fantastical has a backup feature also. Making sure you have a backup of your calendars is just a good idea.