Watch: NASA debunks myths of Mayan apocalypse Fears of an impending apocalypse continue to swell as Earth marches toward its supposed end date: December 21, 2012. But the U.S. government, and NASA in particular, are doing their best to dispel notions that the world is coming to an end. Many of the fears of a coming catastrophe center around the Mayan calender, which inexplicably ends on Dec. 21. As NASA scientists and experts explain in the above video, the Mayans were not predicting catastrophe. Their calendar works just like the ones on your refrigerator: it eventually runs out of days, and a new one starts. In "Why the World Didn't End Yesterday," experts explain the mechanisms behind the Mayan calender. A key point -- and one of the sources of confusion for some -- is that the calender functions much like the odometer in a car. With only so many digits available to display, the numbers will eventually "roll over" and repeat themselves. For example, driving one more mile when your odometer reads "99,999" will turn the numbers back to zero. Of course, this doesn't mean your car suddenly became brand new again. And it doesn't mean the Mayan calender ends. It means a new long-count period is beginning. NASA bases much of the video on the work of Dr. John Carlson, a scientist who has studied the 2012 phenomenon for the past 35 years. Carlson and NASA point out that there is no evidence that the ancient Mayans predicted calamity for 2012. The idea that Dec. 21, 2012 signifies the end of the world would have been news to the Mayans. To them, it is simply the end of a calender period. Furthermore, NASA experts and astronomers from around the world insist that there are no rogue comets or planets in space heading towards a collision course with Earth. As NASA astronomer David Morrison points out, if there really were a world-ending object flying towards our planet, it would already be one of the brightest objects in the sky. Morrison also runs NASA's popular "Ask an Astrobiologist" blog where he fields questions on a wide array of topics. He has had to devote a special section of his website to debunking fears of the apocalypse. For Carlson, Dec. 21, 2012 is not a day of dread. "I have been waiting to experience this day for more than thirty years," he says. Carlson plans on spending the day touring the ruins of Mayan cities in Mexico's Yucatan peninsula.