Every April 1st, pranksters strike with hoaxes, gags, and outlandish claims—but how did this day of trickery begin? Like the best jokes, its origins are a bit murky.

One popular theory points to 16th-century France, when the Gregorian calendar shifted New Year’s Day from April 1st to January 1st. Some people didn’t get the memo—or ignored it—and became the target of jokes. In France, pranksters even stuck paper fish on their backs, a tradition still known as Poisson d’Avril.

Others trace April Fools’ to ancient Roman festivals like Hilaria or to medieval English customs that let peasants mock their lords for a day.

Wherever it started, April 1st has become a global celebration of mischief, from fake headlines to viral internet pranks—keeping everyone guessing, year after year.