We trace the unofficial holiday back to European Spring and New Year's Day festivals, and debunk some false explanations.
April Fool’s or All Fools’ Day is a custom of playing pranks in Northern America, Britain, Scotland (where it is called “Gowk” or “Cuckoo Day”), Australia, New Zealand, France, Germany (“Narrentag”), Belgium, Denmark, Italy, Switzerland, Russia (“Dyen' Doeraka,” literally, “dunce’s day”) and even in Japan.
The precise historical origin of this most lighthearted of unofficial holiday is unknown. The earliest explicit mention of an April Fools joke was found in a French source from 1508, and there exists a Dutch parody on the custom from 1539. But these sources indicate that the custom was already well and universally established. It is probably a tradition that evolved out of many local customs, all having in common the time at which they were kept: the beginning of April.
Some have speculated that the custom imitates Nature playing with our sanity by sending us the fickle April weather. Also weather-related, but more likely as a clue, is the proximity of 1 April to the Vernal or Spring Equinox. The Equinox happens on 25 March, when day and night (“-nox”) are the same (“equi-”). For many cultures this marked the beginning of spring and the new growing and herding season. It was thus celebrated as the beginning of a New Year and an occasion for jubilance.
Thus the Romans dedicated 25 March to Cybele or the Earth Mother with a festival called the “Hilaria” or the "Roman Laughing Day", with games, masquerades and much rejoicing. Though as of 153 BC the official New Year began on 1 January, the time from 1 March to 1 April was also dedicated to Attis, the god of rebirth and trees, and celebrated as the beginning of the New Year.
Also during the Middle Ages, 25 March remained popular as New Year’s Day, even as certain Christian feast days began to vie for pride of place at the beginning of the people’s calendar. In most of Britain, in 525 AD, 25 March was officially made New Year’s Day because it was (also) the day of the Feast of the Annunciation of Christ’s birth to the Virgin Mary (9 months before Christmas). The celebration of Spring usually had to wait till April so as not to coincide with the solemn Holy Week of Easter (though in 2007, Holy Week happens to begin on 1 April).
Unfortunately, this is as far as we can cautiously take our historical explanation of April Fools’. The more historically precise explanations that are in circulation are false. Take the claim that it came about in 1564, when King Charles IX of France made 1 January New Year’s Day. Those who were confused, stubborn or ignorant of the change and still celebrated on 1 April, were called “April Fools”. This is false because, as we saw, 1 April was never a New Year’s Day, in France or elsewhere, and the April Fools custom is older than 1582.
In conclusion, the beginning of Spring is simply a time for celebration, and the custom of April Fools’ certainly fits well with that, and with other such jovial and prank-filled festivals around this time:
And here are some places where the day of pranks is held at other times: