April Fools' Day: it's the best or the worst day of the year, depending on how well you can take a joke.
But how did the annual prankfest begin?
The day's origin is a mystery. The most popular theory is that it began in the 1500s, when France adopted the Gregorian calendar, shifting New Year celebrations from late March to January, National Geographic reported.
People who continued to celebrate the New Year in the spring were allegedly considered fools.
But Alex Boese, curator of the Museum of Hoaxes in San Diego, Calif., disagrees with that theory.
The French legally celebrated the beginning of the year on Easter and it was never really associated with April 1, he told the magazine.
Instead, he believes that the tradition grew out of European renewal festivals in which social norms were inverted, people dressed up and played pranks on each other.
The Museum's website cites the Saturnalia, a Roman winter festival held at the end of December. It was an occasion in which people exchanged gifts, slaves could pretend to rule their masters and a mock king reigned for the day.
Eventually, the Saturnalia became a Jan. 1 New Year's Day celebration, and many of its traditions were incorporated into Christmas.
Meanwhile, a French theory traces the origin of April Fools' Day back to the amount of fish that could be found in rivers when they had just hatched in early April. The young fish were easy to fool with a hook and lure, and they took on the name "Poisson d'Avril" or "April fish."
From there a tradition was born, in which people would try to fool each other to celebrate the arrival of the fish.
The tradition persists to this day, as French people now celebrate by taping paper fish to each other's backs as a prank.
English folklore links April Fools' Day to Gotham, a town in Nottinghamshire, says the U.S. Army's Europe public affairs department.
It was customary in the 13th century for a road to become public property when a king set foot on it.
Gotham's residents heard that King John was coming and spread a false story to keep him from passing through. The king sent a messenger to the town demanding an explanation.
When the messenger arrived, the townspeople were engaged in all kinds of wacky behaviour such as drowning fish and trying to cage birds in roofless enclosures.
It was all a ruse and the king fell for it, declaring the town too foolish to be punished. April Fools' Day, it is said, celebrates the townspeople's trickery.
At least one April Fools' Day origin story is a prank on its own.
In 1983, Boston University tapped Joseph Boskin, a history professor, to act as an expert on the occasion, The Washington Post reported.
Knowing little of its origin, he faked a story to an Associated Press reporter about how the Roman Emperor Constantine I allowed a jester named "Kugel" to run his empire for a day. Kugel then declared a celebration of absurdity on that day each year.
The reporter didn't catch on that "kugel" is a Jewish noodle and that Boskin was just playing around with him. AP ran the story and an editor later chewed out the professor over the phone.
However April Fools' Day came to be, its origin stories are funny enough on their own.
Like this article? Follow our Facebook page Or follow us on TwitterFollow @HuffpostCaLiv