What format does Facebook api return as "birthday"

Question

According to Facebook docs requesting birthday data is done by requesting user_birthday permission set and then the birthday string is stored under birthday in the return array.

What format does it return in, and does the format vary according to users setting?

Formats that I would predict

1990-05-22 // standard
05.22.1990 // USA reverse format
22.05 // User hid birth year
1990 // Getting only birth year without a date
NULL // User hid entire birthday

For me right now is important to determine whether Facebook gives one standard format of birthday value or its format depends on users birthday settings?

Answer 1

The birthday returned by the facebook is a string of the format: MM/DD/YYYY.

Reference.