Below taken from http://en.wikipedia.org/wiki/2012#December

December 21, 2012 — The Mesoamerican Long Count calendar, notably used by the Maya civilization among others of pre-Columbian Mesoamerica, completes its thirteenth b'ak'tun cycle since the calendar's mythical starting point (equivalent to 3114 BC August 11 in the proleptic Gregorian calendar, according to the "GMT-correlation" JDN= 584283). The Long Count b'ak'tun date of this starting point (13.0.0.0.0) is repeated, for the first time in a span of approximately 5,125 solar years.

The significance of this period-ending to the pre-Columbian Maya themselves is unclear, and there is an incomplete inscription (Tortuguero Monument 6) that records this date. It is also to be found carved on the walls of the Temple of Inscriptions in Palenque, where it functions as a base date from which other dates are computed.

However, it is conjectured that this may represent in the Maya belief system a transition from the current Creation world into the next.

2012 is sometimes claimed to be a great year of spiritual transformation (or apocalypse). Many esoteric sources interpret the completion of the thirteenth B'ak'tun cycle in the Long Count of the Maya calendar (which occurs on December 21 by the most widely held correlation) to mean there will be a major change in world order.

Accordingly, several eclectic authors claim that a major, world-changing event will take place in 2012:

The 1997 book The Bible Code claims that, according to certain algorithms of the Bible code, a meteor, asteroid or comet will collide with the Earth.

The 2006 book 2012: The Return of Quetzalcoatl by Daniel Pinchbeck discusses theories of a possible global awakening to psychic connection by the year 2012, creating a noosphere.

Other prophecies and apocalyptic writings and hypotheses for this year include:

Terence McKenna's numerological novelty theory suggests a point of singularity in which humankind will go through a great shift in consciousness.

Some proponents of a peak oil catastrophe place major events in 2012. Richard C. Duncan's book The Peak of World Oil Production and the Road To The Olduvai Gorge claims that the Olduvai cliff will begin and permanent blackouts will occur worldwide. Several studies predict a peak in oil production in or around 2012.