Mod_rewrite - How to tell Google to dynamically delete pages from their index after 7 days

Question

Search engines like to crawl and index webpages or URLs, but what if your webpages/URLs have expired content and you do not want them to be indexed after so many days?

Can you put an expiration in the URL and have mod_rewrite 301 redirect pages after a given expiration date?

Or maybe a cron job to add a 301 redirect header to all expired pages?

Answer 1

Just have the 'expired' pages return a 404? I am pretty sure that when Google encounters a 404, it will remove the page.