Calendar help

Hi I'm new to windows 8 and have decided to fully inform myself on this , however does anyone know why my calendar is showing multiple birthdays sometimes displayed more than once . I know they have been synced from my Facebook and hotmail however I'm struggling to unsung or even manage my calendar so I can delete them !!! Any help ??!?

More than likely, the same data is synced across multiple calendars, and there isn't a good way for the sync client to know they're the same. I have this problem in my Galaxy SIII android calendar.. I have to reset it every so often.