April Fool's Day is the day for pranksters and worse for the victims of those pranks. But have you ever wondered where this tradition originated? There are numerous explanations as to the origin of this day; here are the most popular ones. The most common theory behind the origin of April Fool's Day is the calendar switch that happened in Europe around 1500s. In 1582, Pope Gregory XIII decided to switch calendars, from the Julian to Gregorian calendar. According to the Julian one, New Year's Day fell on April 1 but the Gregorian one had it on January 1. People who were slow to realise this change and continued to celebrate New Year's Day on April 1 were made fun of. They were called Poisson d'Avril (April Fish) and paper fish were stuck to their backs without their knowledge.

Also, the ceremony of washing the lions is believed to be the first recurring April Fools' Day prank ever recorded.

In 1686, British philosopher John Aubrey referred to April 1 as "Fooles Holy Day." Later in 1698, people started tricking others into visiting the Tower of London to see the lions washed. Even tickets were sold for this non-existent ceremony of washing the lions. It continued to be a popular prank for more than a century.

Apart from these, there are other explanations as well. For instance, in Netherlands, the origin of this day is often attributed to the Dutch victory at Brielle in 1572. Another example is of a poem written by a Flemmish poet Eduard de Dene (1561) where he talks about a master who plays a prank on his servant by making him go on silly errands through the day.

Now, go and have fun you pranksters!