Sync Facebook with Google Calendar and CalenGooIf your phone doesn’t support a sync with Facebook via the Android calendar or if you have problems with it, you can also sync Facebook via Google Calendar with CalenGoo:
Sign in to Facebook and click on "Events":
On the right side of the page you should see a link "Birthdays":
Click on that link with the right mouse button and choose "Copy Link Address":
Sign in to Google Calendar and click “Add by URL” on the left under “Other calendars”.
Paste the URL copied address into the URL field and replace "webcal:" with "https:". Then click on "Add Calendar":
Afterward your Facebook birthday calendar should appear as a normal shared Google Calendar. You may have to tap “Sync” in CalenGoo’s menu or “Refresh Android calendars” in the menu under “Settings > Visibility/Download” in CalenGoo to refresh the calendar list and make this new calendar appear.