Wikipedia on the origins of April Fool's Day

The origins of April Fool's Day are unknown, although various theories have been proposed. It is considered to be related to the festival of the vernal equinox, which occurs on March 21. Prior to the adoption of the Gregorian calendar in 1582, it was observed as New Year's Day by cultures as far apart as ancient Rome and India. New Year was originally celebrated from March 25 to April 1, before the Gregorian reforms moved it back to January 1.


The English first celebrated the day on a widespread basis only as late as the 18th century, though it appears to have reached England probably from Germany in the mid-17th century. Its first known description in English originates with John Aubrey, who noted in 1686: "Fooles holy day. We observe it on the first of April. And so it is kept in Germany everywhere."

Some Dutch people mistaking think it may have originated due to the liberation of Den Briel during the Spanish occupation of The Netherlands in 1572, when the geuzen fooled the Spanish lord Alva and were thus able to liberate Den Briel, and the latter supposedly lost his glasses (Dutch: bril).

The custom of playing practical jokes on April Fool's Day is also very widespread and of uncertain origins. The victim of a joke is known in English as an April Fool; in Scots as a gowk (cuckoo or fool); and in French as a poisson d'avril (April fish). It has been suggested the custom may have had something to do with the move of the New Year's date, when people who forgot or didn't accept the new date system were given invitations to nonexistent parties, funny gifts, etc. Originally, April Fool's Day jokes concentrated on individuals (sending someone on an absurd errand such as seeking pigeon's milk) but in the 20th century it became common for the media to perpetrate hoaxes on the general population.


Present Day
The Internet make it difficult to know if it is before or after noon when a hoax is perpetrated. Time zones are different in different parts of the world. It is not even April 1st simultaneously throughout the world. Non-westerners unfamiliar with the April Fool's Day custom may be vulnerable to Internet hoaxes.

In the Spanish-speaking world, similar pranks are practiced on December 28, the Day of the Holy Innocents.

Superstitions
Traditionally, pranks are supposed to end by noon. Those done afterwards are supposed to bring bad luck to the perpetrator. However, this is not universally adhered to, and many of the hoaxes listed below appeared after noon. Anyone who fails to respond to the tricks played on them in the proper spirit of tolerance and amusement will also suffer bad luck. It is also said that being fooled by a pretty girl will be compensated by marriage to, or at least friendship with, her.

Another myth or superstition is that marriage on April Fools' Day is not a good idea for a man, for he will be permanently ruled by his wife. Also, it is believed that children born on this day will experience good luck in most matters, but will only meet with disaster when it comes to gambling.


Hoaxes
Many media organizations have either unwittingly or deliberately propagated hoaxes on April Fools' Day. Even normally serious news media consider April Fools' Day hoaxes fair game, and spotting them has become an annual pastime. The advent of the Internet as a worldwide communications medium has also assisted the pranksters in their work.


Well-known April Fool's Day hoaxes
Kremvax: one of the early Internet April Fool's day hoaxes.


San Serriffe: The Guardian printed a supplement featuring this fictional island (a reference to "sans-serif", a family of typefaces).


Smell-o-vision: The BBC purported to conduct a trial of a new technology allowing the transmission of odor over the airwaves to all viewers. Despite the fact that no such capability existed, many viewers reportedly contacted the BBC to report the trial's success.


Spaghetti trees: The BBC television program Panorama ran a famous hoax in 1957, showing the Swiss harvesting spaghetti from trees. A lot of people wanted spaghetti trees of their own.


Metric time: Repeated several times in various countries over the years, this hoax claims that the time system will be changed to some system where one subdivision is some power of 10 smaller than the next. The idea to metricise time was suggested in France after the French Revolution: see French Revolutionary Calendar.
Tower of Pisa: The Dutch television news once reported that the famous Tower of Pisa had fallen over. Many shocked and even mourning people contacted the television studio.
Television licence: In another year the Dutch television news reported that the government had introduced a new way to detect hidden televisions (in many countries in Europe, one must pay a television licence to fund public broadcasting) by simply driving through the streets with a new detector, and that the only way to keep your television from being detected was to wrap it in aluminum foil. Within a few hours all aluminum foil was sold out throughout the country.

Sidd Finch: George Plimpton wrote an article in Sports Illustrated about a New York Mets prospect who could throw a fastball at 176 mph (the fastest pitchers in baseball barely reach 100mph). This kid was known as "Barefoot" Sidd Finch. He reportedly learned to throw a ball that fast in a Buddhist monastery, and also threw a javelin a quarter of a mile at the British Olympic tryouts. Plimpton said the boy refused to go to the Olympics for fear of hurting someone. Barefoot Sidd was later the subject of a moderately successful book.

Radio Station "Power 106": A Los Angeles radio station "announced" a change from pop to disco music at 7:00 AM, April 1, (1993?). After 12 hours they admitted it was a joke, and switched back to their standard playlist. Within minutes complaints rolled in of "where's the disco?", and the station actually changed formats the next day (and kept disco for a year or two).

Australian Radio Station Triple J: On 1999-04-01, breakfast show co-host Adam Spencer said he had a journalist on the line from overseas where there had just been a secret 9 hour IOC meeting and that Sydney had lost the 2000 Olympic Games. New South Wales Premier Bob Carr was also in on the joke. The story was picked up by mainstream media (including Channel 9's Today Show) before Adam revealed the truth.
Assassination of Bill Gates: many Chinese and South Korean websites claimed that CNN reported Bill Gates, the founder of Microsoft, was assassinated.

Write Only Memory, advertised for sale by Signetics in April of 1972; included in its IC databooks through the late 70s.

Death of a Mayor: in 1998, local radio hosts Opie and Anthony reported that Boston mayor Thomas Menino had been killed in a car accident while in Florida. Menino happened to be on a flight at the time, lending truth to the prank as he could not be reached. The rumor spread quickly across the city, eventually causing news stations to issue alerts denying the hoax. The pair were fired shortly thereafter.
Wheel of Fortune/Jeopardy! Double Switch: In 1997, Pat Sajak, the host of Wheel of Fortune, traded hosting duties with Jeopardy!'s Alex Trebek for one show. In addition to Sajak hosting Jeopardy!, he and cohost Vanna White appeared as contestants on the episode of Wheel that was being hosted by Trebek. White's position at the famed Wheel letterboard was filled by Sajak's wife Leslie.
Comic strip switcheroo: Traditionally, the cartoonists who draw a number of popularly sydicated comic strips will switch roles for a day, each finding someone else to draw their strip for April Fools'.

The Trouble with Tracy: In 2003, The Comedy Network in Canada announced that it would be producing and airing a remake of the 1970s Canadian sitcom The Trouble with Tracy, with Laurie Elliott in the role of Tracy (originally played by Diane Nylund). The original series is widely considered to be one of the worst sitcoms ever produced. Several media outlets fell for the hoax.
Shuttle landing: A Vancouver radio station successfully tricked many listeners in believing that the space shuttle had to do an emergency landing at the Vancouver International Airport.
Howard Stern's April 1st, 2004 show: The show started off with a message stating that due to increased pressure from the FCC, the Howard Stern show had been cancelled, and they played pop songs till after 9:00 am, when Stern came back on and said it was a joke. The pop music was a joke due to the fact that Stern's home station is 92.3 FM K-ROCK, a popular alternative rock station.

Taco Liberty Bell: On April 1, 1996, Taco Bell took out a full-page advertisement in The New York Times announcing that they had purchased the Liberty Bell to "reduce the country's debt" and renamed it to "the Taco Liberty Bell." In a White House press conference, Mike McCurry was quoted as saying that the federal government would also be "selling the Lincoln Memorial to Ford Motor Co. and renaming it the Lincoln-Mercury Memorial." Thousands of people who did not immediately get the April Fool's Day hoax protested.

In 1995, the National Television Station TVM in Malta announced the discovery of a new underground prehistoric temple. The discovery of a mummy eventually led to the announcement that it was an April's Fool joke. This was done during a TV programme conducted by John Demanuele.

Another famous April's Fool Joke was carried out by newscaster Anna Bonanno, which announced that Malta would follow the European continent in changing its motoring rules and motor vehicles would start driving on the right. At the end of the news, it was announced that this was nothing but an April's Fool Joke.
In 2005, one of the largest P2P web sites in China, VeryCD, announced that it had been closed due to some uncontrollable force.
Alternative 3, a fictional documentary broadcast in the United Kingdom in 1977, was originally intended as an April Fool's Day hoax, but due to industrial action it was not broadcast until June. This exposé of international collusion to prepare for global catastrophe fooled many people, and is still the subject of conspiracy theories.
On the first of April, 2004, suprnova.org announced that, owing to a huge surge in Japanese traffic, the site would slowly transition to Japanese, and discontinue its English-language version.