jcyin1 on "[Plugin: W3 Total Cache] Expire header set to 1984??"

I've never really dealt with expires headers before but today I just checked my headers and this is what it says:

Expires Wed, 11 Jan 1984 05:00:00 GMT

Huh?? Where is this expires header set? Can I change this W3Total Cache?

http://wordpress.org/extend/plugins/w3-total-cache/