Duplicate Facebook birthdays in Calendar

[gman eb#AC]

I just recently noticed I have duplicate birthdays entries in my calendar. Some of my friend's birthdays appear twice on their day. Any way to clear this? I recently backed up my contacts and imported them again. Maybe that had something to do with it. Thanks!

 

[BonnyJCooper]

The birthdays that are duplicate in my s planner are automaticly imported from facebook. How can these be deleted so I have the birthday only once?