From my gathering, the failed Nibiru prophecy of 2003, which got pushed off to Dec. 21, 2012 to coincide with the end of the Mayan long-count calendar. Also, a lot of people misinterpreted the completion of a calendar round as the end of time. Look up 2012hoax.org and 2012 on NASA's official website. They explain it best. I would say do a Google search on Mayan beliefs too, but that would turn out a bunch of crap trying to convince you this is real.