comment obtenir de l'utilisateur anniversaire de facebook sdk?

Comment obtenir de l'utilisateur anniversaire par user.getBirthday() ?

Session.openActiveSession(this, true, new Session.StatusCallback() {
      //callback when session changes state
      @Override
      public void call(Session session, SessionState state, Exception exception) {
        if (session.isOpened()) {

          //make request to the /me API
          Request.executeMeRequestAsync(session, new Request.GraphUserCallback() {

            //callback after Graph API response with user object
            @Override
            public void onCompleted(GraphUser user, Response response) {
              if (user != null) {
                TextView welcome = (TextView) findViewById(R.id.textView1);
                welcome.setText("Hello " + user.getBirthday() + "!");
                Log.d("user_birthday","user_birthday:"+user.getBirthday());//user.getBirthday()  this value always is null?
              }
            }
          });
        }
      }
    });

OriginalL'auteur user2185544 | 2013-03-19