April Fool's Day: Beware! Claim: April Fools' Day began in the 1500s when the Gregorian calendar took over from the Julian. Those who forgot the change and attempted to celebrate New Year's (previously celebrated on the 1st of April) on the wrong date were teased as "April Fools." Status: Undetermined. Origins: 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... 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. Arguably the best media-generated April Fool's joke dates from a Richard Dimbleby "news report" aired on 1 April 1957 on BBC's Panorama. It opened with a line about Spring coming early this year, prompting the spaghetti harvest in Switzerland to be early too. Against a video backdrop of happy peasant women harvesting spaghetti from trees, whimsical claims about the foodstuff's cultivation were made in a straightfaced manner. Spaghetti's oddly uniform length was explained as the result of years of dedicated cultivation. The ravenous spaghetti weevil which had wreaked havoc with harvests of years past had been conquered, said the report. More than 250 viewers jammed the BBC switchboard after the hoax aired, most of them calling in with serious inquiries about the piece -- where could they go to watch the harvesting operation? Could they buy spaghetti plants themselves? (For those anxious to try their hand at homegrown pasta, Panorama producer Michael Peacock offered this helpful hint: "Many British enthusiasts have had admirable results from planting a small tin of spaghetti in tomato sauce." Although adults get into the spirit of things (ask any zoo worker about manning the phones on April 1 and having to field endless calls for Mr. Lyon, Guy Rilla, and Albert Ross), it's the children who seem to truly celebrate the day with wild abandon. April Fool pranking between students and teachers is an ongoing battle of wits, with kids favoring the timeworn standards of a tack on the chair, the "missing class" (kids hide under their desks when the teacher is momentarily called out of the room), or a springy fabric snake coiled in a can of nuts. Not every teacher fights back, but those who do are often inventive about it. For more than 20 years, one grade school teacher in Boston comes in early on that day to write the day's assignment upside down on the blackboard. When her curious students arrive, she tells them she did it by standing on the ceiling.