If you haven't heard about the 2012 doomsday predictions, you've been living -- well, probably not quite under a rock, but at least without access to the Internet. Despite the ubiquity of the generic 2012 apocalypse idea, most people don't have a clue where this notion came from.

So where did people get the impression that the world might end in 2012?

One major contender is the Mayan calendar, which, according to some, predicts the end of the world on Dec. 21, 2012. Below, we've gathered some of our favorite explorations of the secrets of the Mayan calendar and its implications for 2012. Click on the links for articles and quizzes pertaining to the Mayan calendar(s), methods for measuring time, and a host of doomsday scenarios:

Big Question: Does the Mayan calendar predict our doom -- will the world end in December 2012?

Big Question: Why did the Mayans use a 260-day calendar?

Big Question: Did the Mayans use multiple calendars?

Top 20 Ways the World Might End

Will the world end in 2012? Take the quiz!

10 Methods of Measuring Time

Julian? Gregorian? Babylonian? What calendar do we use? Take the quiz!