April Fools’ Day mystery explained with theories linking pranks to calendar reforms and folklore

The origins of April Fools’ Day remain uncertain, despite the tradition being widely celebrated for centuries.

According to historical accounts, the custom involves misleading others with "invented or falsified, usually spectacular or fantastic stories, tales or information" on 1 April.

One widely discussed explanation links the tradition to calendar reforms in 16th-century France.

In 1564, King Charles IX introduced a new system that set 1 January as the start of the year, which some people are believed to have continued celebrating the new year on 1 April, becoming the subject of ridicule and pranks.

Another theory dates back to the 16th century and references a failed currency reform linked to the Diet of Augsburg.

According to later reports, speculators who expected changes on 1 April were mocked when the reform did not materialise.

Other possible origins are rooted in literature and religion. Some historians point to medieval Europe, where pranks were already common, while others suggest links to biblical narratives or Geoffrey Chaucer’s 14th-century work The Canterbury Tales.

Records from as early as 1618 reference the phrase “to send into April”, indicating the custom was already established.

Despite the many theories, historians agree there is no single confirmed origin.