April Fools' Day (alternatively April Fool's Day, sometimes All Fools' Day) is celebrated on April 1 every year. April 1 is not a national holiday, but is widely recognized and celebrated in various countries as a day when people play practical jokes and hoaxes on each other called April fools.
In Italy, France and Belgium, children and adults traditionally tack paper fishes on each other's back as a trick and shout "April fish!" in their local languages (pesce d'aprile!, poisson d'avril! and aprilvis! in Italian, French and Flemish, respectively). Such fish feature prominently on many late 19th- to early 20th-century French April Fools' Day postcards.
The earliest recorded association between April 1 and foolishness is an ambiguous reference in Chaucer's Canterbury Tales (1392). Many writers suggest that the restoration of January 1 by Pope Gregory XIII as New Year's Day of the Gregorian Calendar in the 16th century was responsible for the creation of the holiday, sometimes questioned for earlier references