Whoa, this is nuts: Joe Sabia spent the last year and a half creating The Office Time Machine, in which he has organized all the cultural references in The Office by year. For example, above is 1995, and below is 2011...
Look up any year you'd like. It's so addicting!
P.S. How to tell a joke, and Seinfeld reruns.
(Via the always awesome Kottke)