MARK your calendars: The next doomsday is only four years away. But don't worry: Humans managed to survive previous ones without so much as a scratch. Books, websites and a new Hollywood blockbuster from the director of The Day After Tomorrow are capitalizing on the hype surrounding December 21, 2012. This is the last day of a 5,126-year cycle on the "Long Count" Mayan calendar. The Maya, an ancient civilization known for its study of astronomy and its cities in Mexico and Central America, believed that this day would mark a major turning point for the world. According to the Mayan dating system, December 21, 2012, would read "13.0.0.0.0" on the ancient calendar; the number 13 is seen as unlucky in the West. Fears over global warming are feeding the doomsday hype, but no serious Mayan scholar believes the day will bring an end to life on the planet. "The trendy doomsday people... should be treated for what they are: under-informed opportunists and alarmists who will move onto other things in 2013," Mayan scholar John Major Jenkins told CNN.com.