Add Facebook birthdays to windowsphone 8

Steps:

Goto https://www.facebook.com/
Login
Goto events
Goto settings
Export
Right click on export your friends' birthdays, copy link location
 
Goto Google Calenders
Other Calendars
Add by URL, paste the copied link here

settings>calendars>select newly added group
In-front of calendar address, select ICAL, download .ics file

Method I :
     Install add to calender. Download .ics file, open it using th‎is application

Method II:
     Setup gmail in mobile. Synchronous calendar.