Also known as 'All Fool's Day', this is a day where people play tricks on each other and it takes place on 1 April. Most of the tricks involve getting someone to believe something ridiculous, if only for a second. For example, if you tell them 'there is a tarantula on your shoulder' and, startled, they look to see if it's true, it is then that you may shout out 'April Fool'.

In some countries (eg, Ireland and Cyprus) the tradition goes that after 12 noon you can no longer play tricks. In the afternoon, whoever does play a trick becomes the fool. This scenario may have been designed by adults to give themselves a bit of a rest.

There is a rhyme that children recite if anyone attempts an April Fool trick after 1 April:

April Fool is dead and gone,
You're a fool to carry it on.

Origin

One possibility is that the celebration originated in France when the Gregorian calendar was introduced by King Charles IX. Instead of the New Year's celebrations starting on 25 March and ending on 1 April, as they had done previously, the New Year was moved to 1 January. Those that continued to celebrate the New Year in Spring, or simply forgot, became the butt of tricks and jokes and were called Poisson d'avril, meaning 'April Fish'. This must have been so much fun that it spread all over the world and people played tricks on everyone, not just the people who didn't accept the new calendar.

Various Hoaxes

Even if you don't usually read newspapers, make sure you do on 1 April. Some of the articles and adverts are cleverly deliberately incorrect. See if you can spot them!

Some interesting untruths have included:

• The BBC's high-brow current affairs programme, Panorama, claimed that spaghetti grew on trees. (It was broadcast years ago in the days when spaghetti was considered an exotic foodstuff.)

• A report on television about the invention of dehydrated water was broadcast, claiming that all you had to do was shine ultraviolet light onto a powder and it turned into water. The programme included a wonderful demonstration featuring a tap suspended from threads, with a funnel full of the powder on top. A strong light shone into the funnel and a constant stream of water came out of the tap, although it was not physically connected to anything except the threads. Photographs were also shown of an accident in southern France where a lorry-load of the stuff had overturned, causing massive flooding.

• A full-page BMW car advertisement was run on 1 April, 1986, about their new car designed for driving between Great Britain and the Continent. It was both left and right hand drive, had pedals on both the driver's and passenger's sides, had a detachable steering wheel which could be affixed on either side as well as a full set of instruments on each side, the unused one being covered by a lovely walnut panel.

• A mechanism that automatically inflated the car tyres was described by BMW another year. In fact, they run a spoof advert every year.

• The British magazine New Scientist often puts April Fool articles in the issue which comes out near 1 April. The bogus articles have 1 April at the top of the page, while the rest of the magazine has the correct date.

• The Great April Fool's Comic Switch - On 1 April, 1999, saw 27 newspaper comic strip writers swap comic strips for the day. Each strip was written to reflect the style of the new writer and the tone of his usual comic strip.

• A story that a new dinosaur had been discovered by the zoo was put out by The Isle of Wight County Press a couple of years ago. This dinosaur apparently had been found with the remains of a three-sided (not triangular-shaped, but actually three-sided) Roman coin in its stomach.

• The German computer magazine c't is famous for their April Fool's jokes. Back in 1980s, they came up with the following.

  At that time, a Swedish standard for maximum monitor radiation was new and nobody knew whether their monitor was satisfying that standard. Now c't claimed to have found a method to measure monitor radiaton with simple means at home. You had to stick a formatted 5 1/4" floppy disk on your monitor, exactly centred of course, and run a program which generated random images for a minute or so. Then the floppy had to be inserted in the disk drive and a second program had to be run, which supposedly counted the number of faulty sectors (destroyed by the monitor radiation) on the disk and with this computed the radiation level of the monitor. You could even tell the program whether you had a 360K or rather a 1.2M floppy. Of course, all the second program did was display 'April, April' on the monitor.

  Indeed, the true effect of the joke was emphasised when the letters to the editor were printed in the next issue of c't. Someone claimed the second program was defective since it displayed only the aforementiond message and otherwise did nothing. Another reader said the whole method wasn't applicable to his computer since he only had a 3.5" floppy drive and asked if he could adapt the programs so that the whole procedure worked on his computer as well. He even got a reply from yet another reader who said that it wouldn't probably work at all with 3.5" floppies because, unlike the older 5 1/4" floppies, the shutter and other parts of the envelope are made of metal and that would surely spoil the measurement.

• On Paris radio one time, they announced that all of Europe would drive on the left from April 1. This caused absolute pandemonium because those who heard the broadcast drove on the left and those who didn't stayed on the right.

• In 1977, The Guardian published a report about the semi-colon shaped Isles of San Serriffe celebrating their tenth year of independance. It included an interview with the president, General Maria-Jesu Pica, and a competition to win two weeks' holiday in the islands. Surprisingly, only one person complained about the competition closing on March 31 (the day before the article was published).

• Arthur Furguson was a rather remarkable conman who managed to sell Nelson's Column for £6000, Big Ben for £1000, received a down payment of £2000 for Buckingham Palace, leased the White House for $100,000 a year and almost sold the Statue of Liberty for $100,000.

• Albert Einstein's chauffeur once convinced him to let him give one of his lectures on the theory of relativity. He gave it word perfectly, but was almost caught out afterwards when one of the professors asked him a very complicated mathematical problem. Thinking quickly, the chauffeur said, 'The answer to your question is quite simple. In fact it is so easy I'm going to ask my chauffeur to come and answer it for you.'

• On 1 April, 1980, a London radio station announced that low tide had caused the cancellation of hovercraft services from Heathrow airport. Heathrow airport is, of course, well inland.

• On the same day there were some businessmen flying to Belfast surprised to hear the announcement, 'We shall shortly be arriving in Paris'.

King Philipp the Gracious and His Jester

King Philipp the Gracious, in the year 1466, made a bet with his court jester: the jester would earn a bag full of gold if he managed to fool the King on 1 April. Otherwise he would lose his head.

Philipp, clever as he was, met with his jester the day before 1 April and got him drunk. When the jester came back to his senses, he found himself sentenced to death, already on the scaffold, with the executioner's sword already raised.

What the jester didn't know was that the whole thing was an April Fool's trick played on him, the sword wasn't a sharp one and there was a hog's bladder attached to his neck, filled with blood. The sword was swung, blood poured all over the place. However, the jester didn't move an inch. King Philipp, surprised and distraught, and convinced that his ruse had horribly back-fired and that Jester was actually maimed, went to over to recover the jester's remains, whereupon the jester suddenly lifted up his head and requested his bag of gold!