"... The Mayan long calendar will also come to an end on December 21st, 2012, aligned with the Winter Solstice...
The ancient Maya were dedicated stargazers, attuned to the 26,000 year Astrology cycle called the Precession of the Equinoxes. During this cycle the Earth moves through each of the twelve zodiac signs approximately 2166 times each. The Year of the Dragon, which is 2012, is typically a year of big things, be it positive developments or large disasters. It is of intriguing coincidence that the Year of the Dragon and the end of the Mayan calendar fall within the same year.

So will the world end? There is no documentation from a Chinese Astrology perspective that indicates such. The Mayans, along with the Sumerians, Tibetans, and Egyptians believe that this is the end of this age (the age of knowledge), potential to end the world or the coming of a new age (the age of wisdom). Large monuments were left to forewarn society and prepare them for the transition..."

that's just a itty bitty summary of the mystery shrouding 2012

check out this book [link]
to get a better idea of this