I'm pretty sure this problem was caused by the new Facebook app but I've tried all those fixes.
When I sync my google calendar, it's not picking up all my entries. Say I have various events Monday, Tuesday, and Friday. It might only pick up Tuesday's event. And it's not specific which calendar it grabs either, sometimes it gets "work" and not "school" other times its opposite. Here's what I've done so far:
1. Updated to the newest new Facebook app (1.5.32 or something like that)
2. Unchecked "sync calendar"
3. Deleted the CICAL entry in Service Books
4. Cleared out my calendar using DM and resynced my google calendars