How did April Fools’ Day start and why is April Fools’ Day on April 1? tells us that while its true origin remains somewhat of a mystery, historians theorize that the tradition dates back to 1582 when France switched from the Julian calendar to the Gregorian calendar as decreed by the Council of Trent.

Some trace the prank day’s origins to 1582 after Pope Gregory XIII ordered the adoption of  Gregorian calendar which moved New Year’s Day from the end of March to January 1.

Those who were slow to adhere to the new calendar became the subject of ridicule and many jokes. They would often become referred to as “poisson d’avril” (or April fish), someone who could be caught and was gullible.

April Fools’ Day spread throughout Britain during the 18th century. In Scotland, the tradition became a two-day event, starting with “hunting the gowk,” in which people were sent on phony errands (gowk is a word for cuckoo bird, a symbol for fool) and followed by Tailie Day, which involved pranks played on people’s derrieres, such as pinning fake tails or “kick me” signs on them.