The origins of April Fools' Day (All Fools' Day) remain uncertain. Some see it as a celebration related to the turn of the seasons, while others believe it stemmed from the adoption of a new calendar.
Pope Gregory XIII in 1582, ordered a new calendar to replace the old Julian Calendar. This was called the Gregorian Calendar which started on the 1st January (New Year's Day). The theory is not everyone adopted the reformed calendar and refused to accept the new date and continued to celebrate New Year's Day on April 1. The popular believe is followers of the Gregorian Calendar lampooned the traditionalists and send them on "fool's errands." Historically it is unlikely the introduction of the Gregorian Calendar had this effect since the King of France Charles IX in 1564 had decreed the beginning of the year should start on the 1st of January.
Although there is little historical evidence to support the Gregorian Calendar theory it still prevails but other historians believe the origins of April Fool’s day relates to the ancient belief of reversing order. This predates Christianity and is more likely to be associated with celebration of the spring equinox which occurs about March 25th. Many ancient cultures celebrated New Year's Day on or around April 1.
The Romans had a festival day which they called Hilaria to honor Cybele (the great mother) and was held on March 25 involving much rejoicing. From the fourth or fifth century Christians celebrated the Feast of Annunciation the on the 25th of March to commemorate the visit of the angel Gabriel to the Virgin Mary, during which he informed her that she would be the mother of Jesus Christ, the Son of God. In Europe, prior to the introduction of Gregorian Calendar, March 25th was taken as the beginning of the New Year which corresponded to the beginning of the growing season.
It was held to celebrate the resurrection of Attis (son of the Great Mother Cybele) and involved much merriment and wearing disguises. Attis auto amputated his genitals in a fit of folly and many believe he was turned into a pine tree.
In India, Hindus celebrate the feast of Holi with the chief amusement befooling others by sending them on fruitless errands.
The Jewish calendar had Purim, one of the most joyous and fun holidays on the Jewish calendar. It commemorates a time when the Jewish people living in Persia were saved from extermination. It is celebrated sometime in March.
Northern Europeans observed an ancient festival to honour Lud (or Lod), a Celtic god of humour. According to tradition Lud allowed ordinary Celts to play tricks on their revered druids
The church systematically attempted to Christianise the celebration by locating its origin somewhere in Biblical traditions. One version attributed the day’s origin to Noah's mistake of sending a dove out from the ark before the flood waters subsided (thereby sending the dove on a fool's errand). A second story told the day commemorates the time when Jesus was sent from Pilate to Herod and back again. The phrase "Sending a man from Pilate to Herod" (an old term for sending someone on a fool's errand) was often pointed to as proof of this origin theory.
By the Middle Ages, particularly in France, the Feast of Fools (The Festus Fatuous) subverted the rule of social order reversed and power, dignity and impunity were briefly conferred on those in a subordinate position. The central idea seems always to have been a brief social revolution, reminiscent of the Roman Kalends of January, although there is no continuity between the two celebrations. Rooted customs took centuries to eradicate and the Christian Church systematically incorporated many pagan festivals into the Christian calendar. Most experts believe the Christian Feast of Fools had subdeacons occupy the roles normally fulfilled by higher clergy, and the 'fools' symbolised orthodox biblical ideas of humility (e.g. the last being first) and becoming a 'fool for Christ.'
"We are fools for Christ's sake, but ye are wise in Christ; we are weak, but ye are strong; ye are honourable, but we are despised."
Victor Hugo recreated a picturesque account of a Feast of Fools in his novel The Hunchback of Notre Dame (1831), in which Quasimodo serves as Pope of Fools.
The 1st of April was observed in Great Britain by the ancients as a general festival but it took until the beginning of the 18th century before making of April-fools was a common custom. In England, a fool was called a gob, gawby or gobby. The Scots called the custom "hunting the gowk," (cuckoo), and April-fools were "April-gowks. " The cuckoo lays her eggs in other bird’s nests and has no nest of her own. The chick hatches and proceeds to push her adopted siblings out of the nest until they are the only remaining chick. The sound of the cuckoo heralds the beginning of Spring. To be sent to find a cuckoo’s nest would be a fool’s errand.
As all pranksters know April Fools jokes must only be made before midday otherwise the joke is on you.
In France the victim of an April Fool is called a poisson d'avril. Whilst this may have an astrological explanation i.e. in April the sun quits the zodiacal sign of the fish. A more likely explanation is young fish emerge at this time and are easily caught. Poisson d’avril would relate to naivety and French children tape a picture of a fish on the back of their schoolmates, crying "Poisson d'avril" when the prank is discovered.