DigiCal does not sync with Facebook calendar, but it's possible that other (calendar) apps did the syncing with Facebook calendar for you.
- You should be able to disable the Facebook sync in the other apps.
- You can also change the options in the calendar menu in DigiCal so Facebook calendar won't show up in DigiCal anymore.
(Here's a help page explaining how to access the calendar menu in DigiCal.
How to disable Facebook events from syncing to DigiCal.
1. Tap on the Navigation menu and scroll down to your calendars. Tap on the Facebook calendar of the respective account.
2. Tap on Synchronize to toggle it OFF. You can also opt to keep the synchronization ON, but not to display the events of the Facebook calendar by keeping Synchronize ON but turning OFF the 'Show events' option.
3. Facebook Events should now display an unsynced icon next to the calendar.