I've got a better one; it's a little far-fetched, but that hasn't stopped them before. Here goes (you'll need your abacus at hand):
Noah's 120 years; 1 day= 1000 years, therefore 120x365 (approx) = 43800000 / 2520 (of course!) = 17,380 / 4 (horsemen of the Apocalypse) = 4345. The "Jubilee" ("The Watchtower," 1922-NOV-1, Pages 333 & 346) began in 1575 BC); 4345 years from 1575 BC brings us to 2770 (but no year 0, so 2769); and as Armageddon will occur most likely in just a day (360 years), then Armageddon will actually begin around 2409, and be over and done with by 2669. I may have made some errors along the way, but I'm not the only one ... am I ;)