The Mayan calendar begins anew in December 2012, but DC Comics is doing the same this August. The reasoning isn't some complex astro-science way beyond modern man's understanding, but a plot to sell more comics.
DC is rebooting it's universe, starting with Justice League # 1, the series that combines Batman, Superman, Green Lantern, The Flash, Wonder Woman and Aquaman. 51 more first issues will follow, with artist Jim Lee (no relation to Stan of Marvel Comics fame) redesigning the costumes of all the heroes.
Perhaps just as groundbreaking, as USA Today notes: "DC is making all of the re-numbered titles available digitally via apps and a DC website the same day they arrive in comic shops. It marks the first time that a major comics publisher has done so with its popular superhero titles."
DC Comics unleashes a new universe of superhero titles