If we are to believe the Mayan calendar, the end of the world is due on 21 December. But sceptics say climate change or a global pandemic is far more likely to wipe us all out.
The world is set to end again this Friday, according to thousands of YouTube videos and fringe internet sites. The idea has gained so much traction that even Nasa has had to engage the conspiracy theorists.
This is not the first time the world has been predicted to end, but the 2012 doomsday theories have become more widespread than most - supposedly backed by the ancient knowledge of the Mayan civilisation.
Nasa has published a page rubbishing "common beliefs" about how the world will end on Dec 21 2012, explaining "claims behind the end of the world quickly unravel when pinned down to the 2012 timeline".
The US space agency is so certain nothing will happen that is has already published a video - intended for Saturday morning viewing - entitled "Why the world didn't end yesterday" to explain how the scaremongering was a misconception from the beginning.
The truth about 2012 is far less exciting. The Mayans never predicted the world would end, and even if they had, it is not clear this Friday is the date their long-count calendar ends. The Mayans used an advanced calendar which is measured in baktuns, equivalant to 144,000 days. December 21 2012 simply marks the beginning of the 14th baktun.
The 2012 doomsday prophecy credited to the Mayans dates back to the 1970s. New-age followers of Mayanism began to speculate that a cataclysmic event would take place when the calendar ends on the 13th baktun. Boston University Professor William Saturno has pointed out that the Mayan calendar does not end as it is cyclical, and that some calendars mark out "17 Baktuns", which gives us at least another 2,000 years.
The Pyrenees town of Bugarach is the predicted site of an alien encounter that will kick off the armageddon.
This has not stopped some doomsday groups across the world from stockpiling supplies and even weapons, although it is not clear what use they might be if the world did end.
The most popular theories are that a secret planet will collide with earth, solar storms will blast us with radiation, or that a galactic alignment will take place, triggering a series of cataclysmic events.
There is no solid scientific evidence to back up any of the theories, but they have caused panic in some areas. The Pyrenees town of Bugarach is the predicted site of an alien encounter that will kick off the armegeddon - now police have had to be drafted in to keep an influx of believers from climbing the mountain.
Getting it wrong for 2,000 years
This is not the first time the world has got itself into a panic over a dubious doomsday prediction. As early as 634 BC, Romans feared their city would be destroyed after 120 years because 12 eagles had flown over Romulus.
Bishop Martin of Tours announced in 375 AD that the antichrist was born and the world would end by 400 AD. Pope Sylvester II predicted 1000 AD would be the end of days. It did not happen, so in 1284 AD Pope Innocent III announced the world would end 666 years after the rise of Islam.
Italian artist Sandro Botticelli believed he lived during the tribulation in 1504, and was a follower of doomsday prophet Girolamo Savonarola.
In 1524 a group of astrologers in London predicted floods would strike the city as a sign of the start of the end time. 20,000 people abandoned their homes and set up camp in Hampstead and the north Downs. The prior of St Bartholomew even stockedpiled provisions, but it failed even to rain.
In 1524 astrologers predicted floods would strike London as a sign of the start of the end of time. 20,000 people abandoned their homes.
Martin Luther claimed the end would happen in 1600, London's flood was predicted to return in 1624, and in 1657 the Fifth Monarchy Men attempted to take over parliament, believing a final apocalyptic battle was imminent in 1666. Londoners were taken in again in 1761 when a huge earthquake was predicted by William Bell, who was later thrown into Bedlam.
Christian groups repeatedly announced the imminent return of Christ - which would mark the end of days - during the 20th century. Jehovah's Witnesses got it wrong in 1941, 1975 and 1984, and again with the millennium in 1999.
In 1910 many people believed the arrival of Halley's comet would bring the end of the world on 18 May. In 1997 the Heaven's Gate cult claimed the arrival of the Hale-Bopp comet marked the end of the world and that suicide was the only way to "evacuate". 38 people died.
In October of the same year a prediction by an Irish priest that, 6,000 years after creation, the world was due to end, failed to happen.
Scores of theories attached to the end of the millennium, with Nostradamus supposedly predicting the end of the world. But survivalists were left red-faced when the millennium bug failed to bring civilisation to its knees.
Last year Harold Camping, the 89-year-old leader of Family Radio Worldwide, claimed judgment day would happen on 21 May. A number of his followers left their jobs in anticipation, despite Camping's previous predictions passing without incident.
Scientists predict the end
In the short term, greater threats are still posed by global warming, asteroids, global pandemics, argricultural crisis, megatsunamis, artificial intelligence, nuclear war, and the growing resistance of bacteria to antibiotics.
The Centre for the Study of Existential Risk at the University of Cambridge has warned that a reasonable prediction for this century would be intelligence escaping from the constraints of biology, creating the prospect of a robot uprising.