IT has become tradition on the first of April to pull jokes of the harmless variety on those near and dear to us. We plot and we scheme, and often the yuks are funnier in our imaginings than how they play out in reality, but that doesn't stop us from sending the little kid in us out on a rampage. Even the most staid among us have been known to indulge in a practical joke or two, so beware of trusting anyone on that day.

How the custom of pranking on April 1 came about remains shrouded in mystery.

When the western world employed the Julian calendar, years began on March 25. Festivals marking the start of the New Year were celebrated on the first day of April because March 25 fell during Holy Week. The adoption of the Gregorian calendar during the 1500s moved the New Year to January 1. According to the most widely-believed origin for April Fools' Day, those who could be tricked into believing April 1 was still the proper day to celebrate the New Year earned the sobriquet of April fools. To this end, French peasants would unexpectedly drop in on neighbors on that day in a effort to confuse them into thinking they were receiving a New Year's call. Out of that one jape supposedly grew the tradition of testing the patience of family and friends.

But that's only one theory. Others are:
The timing of this day of pranks seems to be related to the arrival of spring, when nature "fools" mankind with fickle weather, according to the Encyclopedia of Religion and the Encyclopedia Britannica.

The Country Diary of Garden Lore, which chronicles the goings-on in an English garden, says that April Fools' Day "is thought to commemorate the fruitless mission of the rook (the European crow), who was sent out in search of land from Noah's flood-encircled ark."

Others theorize it may have something to do with the Vernal Equinox.

Some think to tie in with the Romans' end-of-winter celebration, Hilaria, and the end of the Celtic new year festival.
Wherever and whenever the custom began, it has since evolved its own lore and set of unofficial rules. Superstition has it that the pranking period expires at noon on the 1st of April and any jokes attempted after that time will call bad luck down onto the head of the perpetrator. Additionally, those who fail to respond with good humor to tricks played upon them are said to attract bad luck to themselves.