Centuries ago, Mayan intellectuals created a calendar at least equal to today's most commonly used. Because Catholic priests made certain almost all of Mayan (Codex) history was burned (heretical), we have few factual threads to follow to try to ascertain what this portends for mankind. What little remains seems to predict a unprecedented cataclysm occuring on or after 12/21/2012. Will it, and if so what form will it take; meteor, bombs?
What happens when you get to December 31st of every year? You get a new calendar.
The same with the Mayans. Except they have much longer cycles then our measly 365 day calendar. They were going to create a new one when the time came. Except the Spanish sort of came in and killed the majority off.
Nothing's going to happen. Life will continue as it has on the 22nd. I trust a bunch of physicists and scientist at NASA more than I trust the internet (sorry, internet). http://www.nasa.gov/topics/earth/features/2012.html
If the Mayans knew so much, why did the even bother to go to 2012, since their civilization ended a long time ago? Maybe they just got distracted with some party, war or human sacrifice, and just never got back to it.
Czechbird: A great puzzle for archaeologists and anthropologists is figuring what really did happen to the Inca. There was no gold in what was their domain, so the Conquistadors, except for the ever-present priests trying for conversion or destruction, had no interest. However, much of their civilization was gone before Spanish arrival. What conquistadores did find they destroyed as symptoms of heresy and soulless savages. The Spanish were intellectual midgets as compared to what the evidence from the mysterious Inca had left behind shows.
Orion 1113: The prediction is a part of the (engraved/carved stone) calendar, found by archaeologists, who proclaim that this self-same calendar stops at 12-21-2012. Truly remarkable that these people had such knowledge (of celestial events and calendars) while northern europeans were trying to figure out what to do with fire.
Kernunnos13: Actually the Mayan calendar ended on 12/21, as long ago as 1,000 years, not 12/31. And, what happens in this day and age is we go to our grocery store, hardware store, and probably liquor store and get one appropriate for the year to come.