So mine was created on June 25th 2004, i can see it by the welcome message i got from Google when the account was created.
Looking at Gmail's wiki page, it say that Gmail started working on April 1st 2004. So i got my account less than 3 months after it started.
I still remember that it was by invites and everyone went crazy looking for someone to send them an invite, lucky i had some people that had connections and i got my invite very fast.
So when was your account created?