Yesterday, Blizzard announced that Diablo III will be out on May 15. Reddit seems to have beaten them to the punch. By two months.
In January, Reddit poster SweenWSweens said he used a ridiculous mathematic equation to guess Diablo III's release date. By figuring out exactly what Blizzard community manager Micah "Bashiok" Whipple meant by "early," SweenWSweens guessed that the highly-anticipated action-role-playing game would be out on May 15.
Which happens to be 100% accurate.
We checked the web cache data, and the above post indeed seems to have been from January. And no, SweenWSweens won't tell you when Half-Life 3 will be out. Even the world's most complicated mathematical equations can't tell Valve Time.