April Fools' Day or All Fools' Day, although not a holiday, is a day celebrated in many countries on April 1. The day is marked by the commission of hoaxes and other practical jokes of varying sophistication on friends, family members, enemies, and neighbors, or sending them on a fool's errand, the aim of which is to embarrass the gullible. Traditionally, in some countries, the jokes only last until noon: like the UK, Australia, New Zealand, Canada and South Africa, someone who plays a trick after noon is called an "April Fool". Elsewhere, such as in Ireland, France, and America, the jokes last all day.

Origins

Expand: date=January 2009 thumb|300px|right|Wikipedia's Main Page on April 1, 2007. The featured article write-up purposely confuses U.S. President George Washington with an inventor of the same name. The origin of April Fools' Day is obscure. One likely theory is that the modern holiday was first celebrated soon after the adoption of the Gregorian Calendar; the term referred to someone still adhering to the Julian Calendar, which it replaced. In many pre-Christian cultures May Day (May 1) was celebrated as the first day of summer, and signalled the start of the spring planting season. An April Fool may have been someone who did this prematurely. Another possible origin lies in the fact that when King Charles IX of France officially changed the first day of the year from April 1 to January 1, some of his subjects continued using the old system. In the eighteenth century the festival was often posited as going back to the time of Noah. According to an English newspaper article published April 13, 1789, the day had its origin when Noah sent his dove off too early, before the waters had receded; he did this on the first day of the Hebrew month that corresponds with April. A possible reference to April Fools' Day can be seen in the Canterbury Tales (ca 1400) in the Nun's Priest's tale, a tale of two fools (Chanticleer and the fox), which took place on March 32.

Well-known pranks

• Alabama Changes the Value of Pi: The April 1998 newsletter of New Mexicans for Science and Reason contained an article written by physicist Mark Boslough claiming that the Alabama Legislature had voted to change the value of the mathematical constant pi. This claim originally appeared as a news story in the 1961 science fiction novel Stranger in a Strange Land by Robert A. Heinlein.
• Spaghetti trees: The BBC television programme Panorama ran a famous hoax in 1957, showing Italians harvesting spaghetti from trees. They had claimed that the despised pest, the spaghetti weevil, had been eradicated. A large number of people contacted the BBC wanting to know how to cultivate their own spaghetti trees. It was, in fact, filmed in St Albans.
• Left Handed Whoppers: In 1998, Burger King ran an ad in USA Today, saying that people could get a Whopper for left-handed people whose condiments were designed to drip out of the right side. Not only did customers order the new burgers, but some specifically requested the "old", right-handed burger.
• Taco Liberty Bell: In 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 the "Taco Liberty Bell." When asked about the sale, White House press secretary Mike McCurry replied tongue-in-cheek that the Lincoln Memorial had also been sold and would henceforth be known as the Lincoln Mercury Memorial.
• San Serriffe: The Guardian printed a supplement in 1977 praising this fictional resort, its two main islands (Upper Caisse and Lower Caisse), its capital (Bodoni), and its leader (General Pica). Intrigued readers were later disappointed to learn that San Serriffe (sans serif) did not exist except as references to typeface terminology. (This comes from a Jorge Luis Borges story.)
• DT Day: In 2008 fliers were handed on Brigham Young University campus, saying that the last in a series of dorm buildings being torn down was scheduled to be imploded on April 1. Hundreds of people eagerly turned up to see the implosion, but to their consternation it never happened. The culprits of this prank remain unknown.
• Metric time: Repeated several times in various countries, this hoax involves claiming that the time system will be changed to one in which units of time are based on powers of 10.
• Smell-o-vision: In 1965, the BBC purported to conduct a trial of a new technology allowing the transmission of odor over the airwaves to all viewers. Many viewers reportedly contacted the BBC to report the trial's success. In 2007, the BBC website repeated an online version of the hoax.
• Tower of Pisa: The Dutch television news reported in the 1950s that the Tower of Pisa had fallen over. Many shocked people contacted the station.
• Write Only Memory: Signetics advertised Write Only Memory IC databooks in 1972 through the late 1970s.
• The Canadian news site bourque.org announced in 2002 that Finance Minister Paul Martin had resigned "in order to breed prize Charolais cattle and handsome Fawn Runner ducks."
• Annual BMW Innovations see a new "cutting-edge invention" by BMW advertised across British newspapers every year, examples including:
• Warning against counterfeit BMWs: the blue and white parts of the logo were reversed
• The "Toot and Calm Horn" (after Tutankhamun), which calms rather than aggravates other drivers, so reducing the risk of road rage,
• MINI cars being used in upcoming space missions to Mars,
• Zoom Impression Pixels ("ZIP") to counter new "Slow Cameras" (2000),
• SHEF ("Satellite Hypersensitive Electromagnetic Foodration") Technology, which sees the car's GPS systems synchronise with home appliances to perfectly cook a meal for the instant you return home (2001),
• Marque-Wiper - mini-wipers for each exterior "BMW" logo coming as standard on all future models (2002),
• Tyre Pressure Control - adjust the pressure on the tyres without slowing down (2003),
• IDS ("Insect Deflector Screen") Technology - using elastic solutions to bounce insects off the windscreen as you drive (2004),
• Midnight in the City - An offer for a 15ft x 5ft ceramic "statuette" (sic) by "legendary Prussian ceramist, Loof Lirpa" (2005),
• "Uninventing the wheel" to counter the "EU ban" on right-hand drive cars (2006),
• "BMW Instant Messaging" - using Reactive User Sound Electronic (RUSE) particles to display the driver's words to the car in front on the windscreen (2007),
• Canine Repellent Alloy Protection (CRAP)- a means of discouraging dogs from urinating on car wheels. (2008)
• BMW Magnetic Tow Technology (MTT) - 'This ingenious new system locks onto the car in front via an enhanced magnetic beam. Once your BMW is attached, you are free to release your foot from the accelerator and turn off your engine. The vehicle in front will then 'do the pulling' without noticing any change in manoeuverability. When turning off MTT, we suggest a curteous flick of the headlights to let the obliging driver in front know you are leaving them. It is important to note that MTT does not work without another vehicle. Please email Uve.Vollenvorit@bmw.co.uk (you've fallen for it)' (2009)
• A compact disc available to all BMW owners, which when played over the audio system performed minor service and diagnostic checks; when flipped over it played soothing classical music (Australia).