Loftar has the git-archives since day one, so he could probably find the exact date. We usually celebrate the birthday of "Jorb" and "Loftar", our god characters, which, IIRC, is november 3rd 2007 (I might be off on that, though), rather than the birthday of the game per se. Only legends speaks of a time before the gods: The first being, the lost child (The first time the dude was supposed to walk with animation, he ran straight off into the woods on login), the abominations (Player animations out of sync look... unsound) and the dark forest (Map failed to render, while objects (i.e. the old trees) did).
But OP is right in so far as it has soon been a year since we first started getting users, though. In a way it feels like yesterday, in another way it feels like a different life altogether. I went to Krakow last year in may. I flew out in the morning, and I remember sitting up all night grinding sausages the night before, since we had just implemented the meat grinder. It wasn't long after that that people started trickling in. I remember the first people I introduced to the game. I remember sitting up whole nights just spying at people playing the game. We've come a long way since.

I still distinctly remember the layout of the first hunting camp. There were cows that could be butchered, drying frames and tanning tubs. Quite simply.
