Dec 21 2012 started as a prediction from the Mayans based on their calender.These master astrologers predicted many things through studying the skies. But their not the only ones that predicted this date,there is all so Sumerians, Tibetans, Egyptians, Cherokees, and Hopi.
The scientist of today all so predicted many things that may happen on this day. Most of these are based on the sun changing its polarity. Which could quite possible pull our own earths polls into a polarity change as well.This will be a very dramatic change to the planet and the life on it.
There are many predictios on what is going to happen on this day,So go to these links to see what has been said. The dark star and planet nibiru, Dec 21 Surviving 2012 and planet x,andNostradamus on 2007 to 2012