we have a large form with 3 separate fields for birthday (year, month, day).
To make autofill (f.e. on iOS) work, you have to use specific names on the fields.
According to RFC 3106 (http://www.ietf.org/rfc/rfc3106) there are separate names available for Ecom_Payment_Card_ExpDate_Day, Ecom_Payment_Card_ExpDate_Month and Eom_Payment_Card_ExpDate_Year, but I cannot find the correct values for birthday-fields.
If we'd have a general field for the whole date, it would be "birthday", according to Form field names used by personal data auto-fill in browsers (Safari, Opera)
Thanks Raphael