. One of the earliest known Doomsday Predictions was inscribed on an acient Assyrian clay tablet. Loosely translated, it read, "Our earth is degenerate in these latter days. There are signs that the world is speedily coming to an end. Bribery and corruption are common."
February 1, 1524. London astrologers were convinced that odd planetary activity would give rise to a second Great Flood, causing 20,000 residents to panic and flee to higher ground.
1881. A 16th-century British prophetess named Mother Shipton supposedly wrote that the world would end in 1881, although the publisher of said prophecy, one Charles Hindley, later admitted he made the whole thing up to sell more books. That didn't stop Scottish astronomer Charles Piazzi Smyth from finding "clues" in the Great Pyramids of Giza indicating the world would indeed end in 1881.
May 18, 1910. This date marked the return of Halley's Comet, along with the usual doomsday fears - in this case, the suspicion that the human race would be wiped out by noxious gases in the comet's tail. When Halley's comet swung by Earth on April 29, 1987, doomsday prophet Leland Jensen predicted a collision between it and the Earth that would lead to mass extinction. He, too, was wrong. Coincidental side note: author Mark Twain - born in 1835, another Halley's Comet year - correctly "predicted" he would die when the comet returned in 1910. Sometimes the universe just likes to mess with you.
. A meteorologist named Albert Porta raised the specter again of a rare conjunction of planets that would "cause magnetic current that would pierce the sun, cause great explosions of flaming gas and eventually engulf the earth." It caused a few suicides, alas, before Porta was proven wrong.
March 10, 1982. It was like 1919 all over again with the publication of The Jupiter Effect, predicting that a rare planetary alignment would give rise to earthquakes, or possibly a deadly solar flare.
March – May 1997. Another comet struck fear in the hearts of doomsday disciples in 1997 when Comet Hale-Bopp passed close to Earth. An amateur astronomer mistakenly believed the comet was trailing a mysterious "companion object" and the rumor quickly spread over the fledgling Internet (remember Usenet?). This and a few other rumors combined to the tragic mass suicide of the Heavens Gate cult members.
2060 and Beyond.The great Sir Isaac Newton, in his later years, exasperated by the phonies that abounded in his era, decided to comb through the Bible himself for mathematical proof of the end times. A letter he wrote in 1704 contained his calculations indicating we'll be fine until, oh, at least 2060.