Ideas relating to the 21st of December 2012 have been circulating like a powerful cheese fart for decades now. It seems that the current ideas relating to the Mayan/old Mexican Calendar system, known as the Long Count, began becoming popular with the emergence of Eastern Philosophy and Thought in Western Culture in the 1960's. The Mayan Civilization created a complex calendar which tracks the days in a very similar way to our current calendar system. This calendar system comes to its end on December 21st 2012. The reason for this is still a mystery. Ignoring the fact the the Mayans were a lazy people and most likely got bored one day and stopped making the calendar, all modern anthropologists can do is to theorize what this all means. Some say it is the end of a Great Cycle of the Stars, while others claim it to be a sign that The Rapture is at hand, and yet other theorize that the Mayans accidentally sacrificed their calendar maker causing great Bawww throughout the smelly bean filled land. Humans have a tendency to believe strange things, and as history has shown us are willing to embrace seemingly crazy ideas. The sane minded expect that once people awaken on 12-22-2012 they will find the Mexicans claiming "the Mayans did it 4 tha lulz" then there will be a spicy salsa and bean dip parade with taco floats and a virgin will be sacrificed, if one even exists in Mexico. (I doubt it, since all beaners rape anything with a hole no matter what their age is.)
Here is the source, but be careful, its not really safe for work.