The U.S. government wrote a helpful blog post on Monday titled, "Scary Rumors About the World Ending in 2012 Are Just Rumors."

The post on USA.gov says NASA scientists have received thousands of letters from people convinced that the world will end on Dec. 21, based on a misunderstanding of the ancient Mayan calendar that's been promulgated in doomsday message boards online. Some people think a giant comet will strike Earth that day, others that we are about to collide with another planet. A NASA scientist said he's received several letters from young people contemplating suicide because they believe the apocalypse is coming.

"The world will not end on December 21, 2012, or any day in 2012," the post says.

NASA released a video earlier this year explaining that the Mayan calendar does not actually predict the end of the world on Dec. 21, and that the myth that the planet "Nibiru" is heading toward Earth is easily disproved because astronomers have detected no such planet. America is not alone in trying to placate nervous doomsayers. The Russian government has made similar assurances to its people that the end of the world is not nigh, and authorities in France are planning to block access to a southern mountain which believers think could serve as a mystical place of refuge on Dec. 21.

Some doomsday groups are capitalizing on the fear by spreading the Dec. 21 myth online. A Belgian amateur astronomer named Patrick Geryl has set up an online community for people who follow him and believe the world will end in three weeks. He tells followers to stockpile 15 to 20 pairs of shoes and to be in good physical shape. Geryl declined an interview request, saying over email, "No time for interviews. ... Want to enjoy last weeks of our civilization."