In the UK, an April Fool joke is revealed by shouting "April fool!" at the recipient, who becomes the "April fool". A study in the 1950s, by folklorists Iona and Peter Opie, found that in the UK, and in countries whose traditions derived from the UK, the joking ceased at midday. A person playing a joke after midday is the "April fool" themselves.
In Scotland, April Fools' Day was traditionally called 'Huntigowk Day', although this name has fallen into disuse. The name is a corruption of 'Hunt the Gowk', "gowk" being Scots for a cuckoo or a foolish person; alternative terms in Gaelic would be Là na Gocaireachd 'gowking day' or Là Ruith na Cuthaige 'the day of running the cuckoo'. The traditional prank is to ask someone to deliver a sealed message that supposedly requests help of some sort. In fact, the message reads "Dinna laugh, dinna smile. Hunt the gowk another mile." The recipient, upon reading it, will explain he can only help if he first contacts another person, and sends the victim to this next person with an identical message, with the same result.
In England a "fool" is known by different names around the country, including a "noodle", "gob", "gobby" or "noddy".
In Ireland, it was traditional to entrust the victim with an "important letter" to be given to a named person. That person would then ask the victim to take it to someone else, and so on. The letter when finally opened contained the words "send the fool further".
In Poland, prima aprilis ("1 April" in Latin) is a day in which many jokes are told; various hoaxes are prepared by people, media (which sometimes cooperate to make the "information" more credible) and even public institutions. Serious activities are usually avoided. This conviction is so strong that the anti-Turkish alliance with Leopold I signed on April 1, 1683, was backdated to March 31.
Danes, Finns, Icelanders, Norwegians and Swedes celebrate April Fools' Day (aprilsnar in Danish; aprillipäivä in Finnish). Most news media outlets will publish exactly one false story on April 1; for newspapers this will typically be a first-page article but not the top headline.
In Italy, France, Belgium, The Netherlands, and French-speaking areas of Switzerland and Canada, April 1 tradition is often known as "April fish" (poissons d'avril in French, aprilvis in Dutch or pesce d'aprile in Italian). This includes attempting to attach a paper fish to the victim's back without being noticed. Such fish feature prominently on many late 19th- to early 20th-century French April Fools' Day postcards. Many newspapers also spread a false story on April Fools' Day, and a subtle reference to a fish is sometimes given as a clue.
In India, there have been numerous references to April Fools' Day in both cinema and popular literature and people are jovially associated with the day. However, this is not any intrinsic part of India's ancient culture..
In Lebanon, an April Fool joke is revealed by shouting "كذبة ابريل !" (which means "Aprils fool!") at the recipient, who becomes the "April fool".
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And since Easter falls on April 1st this year...