It’s the day when pranksters get their adrenaline rushes, and those who are gullible walk around in terror. That’s right, folks, it’s April Fools’ Day. From telling their parents before they’ve had their coffee that their shoelaces are untied, to putting “kick me” signs on each other’s backs, everyone is familiar with the first of April. Fitting to the nature of the holiday, no one knows the true origins of April Fools’ Day, although there are many different theories and marks in history that show how the holiday has been celebrated. April Fools’ Day is believed to have begun around the 16th century in northern Europe and then grew so popular that it made its way to Great Britain.

Since the first of April was so close to the vernal equinox, Romans and Hindus in ancient days would use this day as the mark of the New Year. In 1582, the start of the year changed to January 1 under the Gregorian Calendar. Some didn’t like the idea that the first of April was considered the beginning of the year, so they made it “fools’” day to make fun of those who didn’t switch to the new calendar and were clinging to old traditions.

In Europe, there was a celebration called the Feast of Fools where jokes would be played on other people, similar to what happens here in America. Today, Europeans typically refer to the holiday as “Poisson d’Avril” or “April Fish.” Kids are notorious for running around and taping pictures of fish on their friends’ backs.

One theory of the origin of this holiday is credited to a history professor at Boston University; according to the professor, a group of jesters challenged the Roman emperor and said they could run the empire better than he could. After being printed in multiple papers by the Associated Press, it was discovered that this was an April Fools’ joke played by the professor that made it all the way to print media.

In Great Britain, legend has it that there was a town named Nottinghamshire that was known for having a clan of fools hanging around. When a king was claiming property for his territory, he travelled through the town. The fools met the soldiers when they came into town for the king to force entry, but the soldiers found these crazy people wreaking havoc in the town, so the king declared the town was too silly to claim.

Some say that spring is pulling a prank on humans by giving the world unpredictable weather during the season. Those who are superstitious say that if pranks continue past noon on April 1, bad luck will ensue for whoever continues to prank. Here’s one for the fellas out there: if a guy is tricked by a pretty girl, according to these superstitions they will end up married.

While there are many intriguing theories of how April Fools’ Day started, the one backed with the most evidence shows that it all started at Camp Walden when a couple of teenage girls put their friends’ beds on top of their roofs. In retaliation, on the night of April 1, the victims covered their pranksters and the floor next to their beds with honey while they were sleeping, covered the room with spider webs made out of yarn and set up a booby trap filled with water balloons to fall down and splatter all over everyone. From this pranks continued to ensue every April 1, which eventually gained the name of April Fools’ Day.

Sources: Britannica.com, Hoaxes.org, Infoplease.com, Wilstar.com