title: what should be HTTP status code for credentials Expired error/exception?
body: <p>I am developing RESTful APIs, I have implemented token-based authentication, where token digest is prepared using time-stamp. Now when request comes to API server, I am checking if the supplied time-stamp is invalid ( i.e. date-time from future/past is specified) then am throwing error message indicating that "future token detected" or "token has expired". I need to attach HTTP status code I am confused about which status code is suitable for this situation?</p>
  
  <p>I have gone through the status codes available (<a href="http://www.restapitutorial.com/httpstatuscodes.html" rel="noreferrer">ref1</a>, <a href="http://robertlathanh.com/2012/06/http-status-codes-401-unauthorized-and-403-forbidden-for-authentication-and-authorization-and-oauth/" rel="noreferrer">ref2</a>) so far, I think, using 400 'bad request' will be suitable here instead of 401 'Unauthorized' and 403 'forbidden'  status codes.</p>
  
  <p>what do you think guys?</p>