On April Fools' Day, 1 April, it's the custom in several cultures to play practical jokes and to spread hoax stories.
Where and when did this custom originate?
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No one really knows for sure but the idea is in France in the 1500s New Year's celebrations would start a few days before then end on April 1st. When the date changed to January 1st people who still celebrated on the old date would be made fun of as April fish. A few centuries later people would try to stick a paper fish onto someone's back, without them noticing, as a prank. It seems that over time people forgot all that and just stuck to pranks and other silliness.
Origin of April Fools' Day or April Fool's Day1:
A disputed association between April 1 and foolishness is in Geoffrey Chaucer's The Canterbury Tales (1392).
In 1508, French poet Eloy d'Amerval referred to a poisson d'avril (April fool, literally "April's fish"), possibly the first reference to the celebration in France.
Some writers suggest that April Fools' originated because in the Middle Ages, New Year's Day was celebrated on March 25 in most European towns, with a holiday that in some areas of France, specifically, ended on April 1, and those who celebrated New Year's Eve on January 1 made fun of those who celebrated on other dates by the invention of April Fools' Day.
So, the earliest date seems to be circa 1392.
1 Wikipedia contributors. (2021, February 9). April Fools' Day. In Wikipedia, The Free Encyclopedia. Retrieved 14:02, February 13, 2021, from https://en.wikipedia.org/w/index.php?title=April_Fools%27_Day&oldid=1005743216