Format for x-fapi-auth-date

Question

What date format applies for x-fapi-auth-date?

Answer

Use of this field is specified in the normative standards, in this instance the FAPI read profile. Specifically in section 6.2.2:

"3. may send the last time the customer logged into the client in the x-fapi-auth-date header where the value is supplied as a HTTP-date as in section 7.1.1.1 of [RFC7231], e.g., x-fapi-auth-date: Tue, 11 Sep 2012 19:43:31 GMT;"