I joined April 21, 2012. I know this because I made a forum account thinking that you were required to have one to play on the servers. (This wasn't uncommon, and though it's less so now, still it pretty prevalent.)
I think my first forum post was an application to the first Hell Games actually
(I have applied to every Hell Games excluding one, and still have not been accepted... ;-; wait a minute...what happened to the Hell Games anyway? nvm I'm getting off topic..)
I checked both MLG and Nub because why the heck not as well.