What happens if the origin web server sets the expires value in response header as a time which is passed relatively long ago?

What happens if the origin web server sets the expires value in response header as a time which is passed relatively long ago.

For instance, consider current time is Fri, 25 Jan 2013 GMT, and the expire header is set as -->

Expires: Thu, 01 Dec 1994 16:00:00 GMT

How will the client respond for the above instance?

Any help would be appreciated