The issue is with Facebook or BB10 it depends on how you look at it.
If you try and edit the Facebook birthday you will notice that it is imported as the mm/dd/yy
Since most people don't add the year to their birthday on Facebook I assume they substitute /00 for kicks. BlackBerry 10 is interpreting this as 1900 not 2000. I think this is somehow where the issue lies.
For me the date shows up one day early in the contact app but the reminder and calendar display and act correctly.
So for example My friends contact, her birthday is July 11/1993 which is what I have programmed into the contact. Facebook imports 7/11/00 yet displays July 10.
If I go to the calendar app her birthday is shown on July 11. If I remove all other calendars except Facebook just to be sure the Facebook entry still shows up on July 11 where it should.
BlackBerry 10 has issues with how they treat two digit dates in the contact app if the calendar app manages to get it right.
Posted via CB10