Normally Squid emits the Date header as received from the origin server and a Age header indicating how long the object has been in the cache (somewhat buggy thou, as revalidation only changes the Age header, the old Date header is still kept).
However, in an accelerator it is often wanted that the accelerator seemingly acts as the origin server, generating it's own Date header (with no Age header).
Note: If this is done then the origin server and accelerator MUST be clock syncronized. Having a clock difference more than a few seconds is likely to cause unwanted (bad) sideeffects in freshness validations..
