When it comes to the end of the world, the Jehovah's Witnesses are not exactly known for being eternal optimists. They wrongly predicted doomsdays in 1874, 1881, 1914, 1920...and countless times since. Their most recent date to come and go without a bang was 1994.

Members of the Heaven's Gate cult believed they had to shed their earthly bodies before catching a celestial ride on a spaceship in the comet's tail. In an organized ritual, 39 members committed suicide and were found lying beneath purple shrouds in identical black outfits and new sneakers. They believed the apocalypse would closely follow their departure. In the end, Hale-Bopp was right on schedule, but the apocalypse was not.

An age-old tablet from the cradle of civilization contained a carved warning that disobedient brats, rampant corruption and lots of men wanting to write books clearly indicated the world was fast coming to an end. This was 2800 B.C. It is obvious that the writer of the tablet was a bit off on his dates as, millennia later, obnoxious tweens, widespread fraud and best-seller lists go on, as does the world.

Before the top-secret Trinity atomic bomb test, some scientists speculated that the nuclear reaction could ignite the atmosphere and kill every living thing on Earth. The probability of a global conflagration was calculated to be infinitesimally small and they (gulp) pressed the button.

The famous director of Citizen Kane scared the bejesus out of a bunch of East-Coasters who tuned in late to a radio play of "The War of the Worlds." Having missed the opening disclaimer, they thought news reports of a Martian attack were the real deal. Mass hysteria ensued, with people rushing to their families or their churches to await the death rays. Welles, meanwhile, was undeterred and soon moved on to terrifying another segment of the population: Hollywood producers.

The French seer's vague quatrains have been a never-ending source for future doomsday prognostications and hysterical 20/20 hindsight. Most recently, he was believed to have predicted the events of 9/11, but as with anything else surrounding that day or Nostradamus himself, the theories are shaky at best.

On August 9, 2006, Beck said August 22 could be "the day that Israel might be wiped off the map, leading to all-out Armageddon." In his correction, Beck said the date was clearly off, but to keep checking your local listings for the Eastern-standard end-times.

In his later years, the great scientist searched the Bible for mathematical proof of the end times to refute all the crazy people predicting the apocalypse willy-nilly. In a 1704 letter, Newton scribbled calculations that he said prove the world is safe from annihilation until at least 2060. That's what's called a smackdown, 2012.

Far more than a handful of believers sold all their earthly possessions when minister William Miller predicted the rapture for between March 21, 1843 and March 21, 1844. Newspaper reports of the time claim he had about 100,000 followers who quit being productive citizens in apocalyptic anticipation. When the date passed, Miller rescheduled for October but was wrong again. Many, many people were bummed by the lack of brimstone and left the movement.

This apocalypse averted was worthy of the worldwide sigh of relief that followed its peaceful resolution. The October 1962 Cold War standoff began when U.S. spy planes discovered Soviet nuclear missile sites being built in Cuba, which sits just 90 miles off the American mainland, and President Kennedy ordered a Naval blockade of the island. The world was on the brink of a nuclear war until the Soviet Union agreed to disarm and dismantle the missile sites, contrary to the wishes of the Cuban government. In return, the U.S. secretly agreed to disarm nuclear sites in Turkey.

Some feared the giant high-energy particle accelerator, which went online at the European Organization for Nuclear Research in 2008, might create a tiny black hole that would consume the entire Earth. So far, no matter has been sucked into oblivion as a result of the subatomic head-on collisions, but here's hoping that "light jazz" is first to go.

Chicago housewife Dorothy Martin claimed she had been in touch via "automatic writing" with aliens from the planet Clarion, who told her they were en route to rescue her and her handful of followers from a massive flood to occur on December 20, 1950. To study what happens when a prophecy fails to materialize, social psychologist Leon Festinger infiltrated the believers, many of whom had quit their jobs and sold their homes. When the mother ship and flood were both no-shows, Martin announced that she had received an alien dispatch that humanity was saved by their faith. Changing her name to Sister Thedra, she went on to proselytize about the intergalactic miracle and Festinger developed his theory of cognitive dissonance to explain their behavior. (The flood pictured occured in Topeka, Kansas, six months later.)

In 1919, meteorologist Albert Porta scared a lot of folks when he said the coming alignment of six planets would create a magnetic current that could pierce the sun and create solar flares large enough to engulf the Earth. The only calamitous effect was to Porta's career when nothing happened.

In this best-selling book, astrophysicists John Gribbin and Stephen Plagemann revived Porta's planetary convergence theory with apparent disregard of the fact that it had proved false. Their dire predictions of a March 1982 lineup of seven planets would, they claimed, lead to increased sunspot activity and a sudden reversal in the Earth's rotation that would trigger major earthquakes. The only result of this seven-planet conspiracy? A slightly higher tide.

Multiple English sources had this pegged as an earth-shattering year. A 16th-century British prophetess named Mother Shipton supposedly wrote: "The world to an end shall come; in Eighteen Hundred and Eighty One." The verse was included in an 1862 collection published by Charles Hindley, who later admitted to inventing the prophecy to boost sales. Then Charles Piazzi Smyth, a respected Astronomer Royal for Scotland, claimed he discovered clues in the Great Pyramids of Giza that pointed to 1881 as the world's end. Teacups clinked nervously across the British Isles until 12:01 a.m., January 1, 1882.

The largest and most visible comet since Halley's 1910 fly-by, the 1974 passing of this giant iceball was deemed a harbinger of doom for, curiously, only the United States. Even more suspiciously, these claims were laid by David Berg, leader of the Children of God cult. Followers hightailed it to communes outside the country to escape this highly specific and very poorly diagnosed apocalypse.

Computers were expected to run amok at the turn of the millennium because they couldn't recognize the 00 at the end of the year 2000. Experts predicted nuclear war when early-warning systems malfunctioned, an economic calamity as financial software failed, and an all-around grinding halt to our tech-dependent lifestyles. In the end, most computers were updated in time or failed to adhere to the alarmists' predictions.

The calendar flip from 999 to 1000 caused some jitters, but not the rampant panic of Y2K. The Gregorian calendar wasn't yet in widespread use, many people were illiterate and there was no Internet, so most people were uninformed about the need to be terrified until way after nothing happened.

1000 + 666 = our number's up. Fuzzy and fearsome math is often used to calculate the exact date of the end of the world. The scary equations frequently involve large round numbers, the digits of the beast and portents to the power of yikes! Although it was the year of the Great London Fire (pictured), life as we know it went on.

All hell broke loose when the deadly gas cyanogen was discovered in the flying iceball's tail, with French astronomer Camille Flammarion warning that life on Earth would be imperiled when it passed by. Business boomed for anti-comet pills and gas masks and, in 1910, thousands took to the streets and their church pews, praying to live through the comet's strike. But it left Earth alive and kicking; that is, with the exception of Mark Twain, who was born soon after the previous visit by Halley's Comet and had now been given to its dust.

The Maya Long Count calendar completes a 5,126-year cycle on December 21, 2012. With the winter solstice and a rare alignment of the Sun with the center of the Milky Way galaxy also on the docket, this has become the doomsday du jour. Most media outlets have snubbed scholars who insist the end of the cycle only means an extra awesome New Year's Eve (if you're an ancient Mayan like the ones who lived at the pictured Tikal, Guatemala, ruins) and that the date may have been miscalculated and passed already. Go ahead and stockpile, spend quality time with your family and cower if you must, but definitely don't quit your day job.