How do I uninstall BusyCal?

To uninstall BusyCal along with its database, launch BusyCal while holding down the option key to display the Startup Options dialog, then select Reset BusyCal and click Continue. Resetting BusyCal will delete the BusyCal database, and quit. All of your calendars will be preserved in iCal, iCloud, Exchange and/or Google.

Next, open the Applications folder, drag BusyCal.app to the Trash, right click and Empty it.

macOS may continue to display the BusyCal menu app (and may continue to show alarms) even after deleting the app. To stop this, open Activity Monitor.app, search for BusyCal, select the process still running and click on the (x) button on the Toolbar to quit the process. If the main app is still somehow installed or found on disk elsewhere (such as in the Downloads folder), macOS may try and launch the menu app from there again. You'll have to find and delete all copies of BusyCal.app on disk and manually force quit the menu app.