99% sure it was October 26, 2007.
The news says "See you Monday!", so it's a Friday. The news for 1001 comments that Leopard is out. According to
the Internet's #1 source of mostly-accurate information, Leopard was released October 26, 2007. (Which
was a Friday.) It was kind of a big deal, so almost everyone who cares about that sort of thing would know and be excited about its release, so it's safe to assume that news post wasn't too far behind Leopard's release.
You could also work the numbers out by finding the number of comics elapsed, then dividing by 5 (the number of updates per week) to get the number of weeks elapsed, then go from there. But I think it's easier to go by the news posts if they mention something you can find a concrete date on. (But for some, math is
delicious the only solution.)
