Alternately, if you do not want to use Cache-Control headers, you can set an Expires header instead. An Expires header is useful if you need to be really specific as to when your page expires. The general format for an Expires header is:

Expires: Tue, 25 Jan 2007 10:30:00 GMT

The date and time must be presented in the HTTP date format, and it must be in Greenwich Mean Time.