So a little while back on Discovery channel or something of the like I watched a documentary on the Mayans regarding how and why there have been thousands of stones engraved with humanoid alien like figures, also dinosaurs. It concluded that aliens may have come in contact with them, simply said. They also invented the gregorian style calendar which, in their version was said to abruptly end on Dec 21st 2012. So what if the Mayans were informed by the aliens the world would end on the specified date, and the gregorian calendar was then invented to keep track of time so we would know the exact time and date they would return.
Im not saying this is my belief, its just something I thought of while pondering the 2012 conspiracy.