Step 1: Use the Birthday Exporter facebook app http://apps.facebook.com/ical_exporter/
Step 2: Save the ICS file that it generates
Step 3: Open up the ICS file in a text editor. Preferably one that can record macros. To each
VEVENT entry in the ICS file (demarcated by
END:VEVENT) add the following two tags:
Step 4: Go to the Windows Live Calendar that is linked to your Windows Phone account. Click on “Subscribe”, click “Import from an ICS file” and then import the file into your calendar.
Step 5: Wait a while. Your calendar on the phone will reflect the new entries shortly
Note 1: Step 3 is important, otherwise you will be shown as busy on the calendar, and windows phone will report conflicts on the calendar (shown with two arrows pointing towards each other diagonally)
Note 2: Currently windows phone only syncs the primary calendar of the live id. If you don’t want to mess up the primary calendar, create a new throwaway live id and import it into that calendar. Add that account on your phone, and choose to sync only the calendar.