However, having Easter and April Fool’s on the same day may be more than coincidence. These two dates are linked for a very Christian reason. 

It is hard to pin down the true origins of this international day of practical jokes, but one of the most popular theories of the origins of April Fool’s Day traces back to the Catholic Church in the 16th century. 

Pope Gregory XIII instituted the Gregorian calendar in 1582 to replace the Julian calendar established by Julius Ceasar in 46 B.C. Because the Roman emperor’s old system miscalculated the solar year, Easter fell further away from the spring equinox with each passing year. The pope’s reformed calendar attempted to restore Easter to the time of year that it was celebrated when introduced by the early Church. 

The transition between the calendars was not a smooth endeavour. The Gregorian calendar moved the new year from the end of March to the first of January. People who continued to celebrate in March were said to be mocked as “April fools.” 

Alexander Andrée, professor and co-ordinator of Medieval Studies at University of St. Michael’s College at University of Toronto, said the transition from the Julian to the Gregorian calendar was a messy time in the Middle Ages. 

Although many Catholic countries, such as Italy, Spain, France and Poland, adopted the Gregorian calendar fairly quickly, far more nations resisted. The last country to adopt the calendar was Turkey in 1926. 

For Pope Gregory XIII, Andrée said the most important goal for the Church was to figure out the day of Easter. 

“I’m sure there were lots of confusion when that happened,” he said. “I think the most important thing for Christians in the Middle Ages was to calculate the dates of Easter and they did that with astronomical observations and tables.” 

Andrée said there are many theories that link April Fool’s Day and the Christian traditions of Easter. Another theory he encountered traces back to the  medieval French tradition called “Poisson d’Avril” or “April Fish” — which is still the French term for April Fools’ Day today.

“In one of the oldest forms that this trick took, several persons would conspire to send the victim on a fool’s errand from conspirator to another... so the person with the fish on his back would be sent out on a fool’s errand,” said Andrée.

The April Fish has evolved across other countries in Europe and is now more commonly recognized as the “Kick Me” sign gag. 

Andrée said that this holiday was held as a counterpart to a religious feast celebrated in medieval France. April 1 was marked in Christian tradition as the day that Jesus began His public ministry, which Andrée said might explain the fish as it was an early symbol of Christ. 

“On the one hand you have the tradition that Christ began His ministry on April 1 and then of course, that’s the day that you begin to joke with each other. It’s a typical medieval thing,” said Andrée. 

He said this duality between serious and fun can be seen in many different forms during the Middle Ages. In studying serious theological texts, Andrée said it was common to see small drawings and caricatures in the margins. 

If another theory is to be believed, April Fool’s Day might be traced back far earlier than the 1500s. From the fifth to 16th centuries, a medieval festival called Festus Fatuorum, or Feast of Fools, evolved out of a Roman pagan tradition of Saturnalia. According to folklore, Saturn (the Lord of Misrule) reigned on this day of the winter festival, which allowed people to play with reversing social roles and dressing in costume. 

American folklorist Jack Santino wrote that Church officials originally encouraged the celebration because they believed it helped “release pent-up anti-clerical sentiment among the people.” But by the 15th century, the feast became too raucous and was banned. 

“They call it a ventilation feast. You kind of ventilate the frustrations you have over the years with people in high positions and you get a chance to take it out on them as it were,” said Andrée. 

Earlier still, there are theories that suggest biblical roots for April Fool’s Day. 

One theory traces the tradition to the story of Noah’s Ark. April Fool’s is thought to commemorate when Noah sent a bird out on a “fool’s errand” to search for land. 

A second theory suggests that the date points to the story of Jesus being sent from Pilate to Herod and then back again to Pilate. 

Suffice to say, April Fool’s has been a part of Christian culture and world culture for a long time.