Why are we asking this now?

Because it's that day again: after another boring 364 days of sober honesty all round, the beloved annual festival of practical jokery is upon us once more. If you're reading this before midday, it's your one chance in the year to pull the wool over somebody's eyes with impunity.

So why are the rules different on 1 April?

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The stories surrounding the origin of April Fool's Day are widely various and it's hard to be certain about the truth – especially when you consider that people feel they have carte blanche to make things up when it comes to this subject. Still, whether it's true or not, one popular tale dates the tradition to 1564, when France formally changed its calendar to the modern Gregorian version, and thereby moved the celebration of the New Year from the last week of March to 1 January. In this version of events, those who continued to celebrate the end of New Year's Week on 1 April were derided as fools – or, as they are known in France, poissons d'Avril. The problem with that story is that the adoption of the new calendar was a gradual process that took place over a century, making the ridicule of those who continued to celebrate the old date seem unlikely.

Are there any other explanations?

Lots. Alex Boese, the curator of the online Museum of Hoaxes, points to a worldwide tradition of "renewal festivals", which can be found in many different cultures, and frequently involve ritualised chaos. It seems likely that the modern version is a mutated variant of these predecessors. In ancient Rome, for instance, the Hilaria festival celebrated the resurrection of a demigod with the donning of disguises; and the medieval Feast of Fools, wherein a Lord of Misrule was elected to parody Christian rituals, endured centuries of church censorship.

There is even a British legend, which places the festival's origin in the Nottinghamshire town of Gotham. The story goes that in the 13th century, the town's residents heard that King John could claim any road on which he stepped as his property and so they accordingly refused the monarch entry. When his soldiers arrived to force their way in, the residents of Gotham pretended to be lunatics, and King John decided that their madness meant that the punishment that would have otherwise been meted out would be inappropriate. According to this story, April Fool's Day celebrates their sneakiness. It is, unfortunately, totally uncorroborated by hard evidence.

Why does the tradition expire at noon?

That feature probably relates to the customary boundaries of the old renewal festivals, which limit the mayhem to a very strict timeframe. The source of Britain's deadline might be the 17th century's well-named Shig-Shag day, when celebrants put oak sprigs in their hats to show loyalty to the monarchy, in reference to Charles II's hiding in an oak tree. Those who failed to observe the custom could only be ridiculed until midday. These days, anyone who plays a prank after noon is supposedly an "April fool" themselves; this nice observation may not seem so crucial to anyone who has been custard pied at 12.01pm, but it distinguishes our version of the ritual from that found in other countries.

Do people really still play April Fool's tricks?

The problem with the modern April Fool's is that pranks are so thoroughly embedded into our culture that a day specifically devoted to them can almost seem redundant. Television shows like Beadle's About and Candid Camera and their successors have made most of us so inured to the prospect of a practical joke that whenever anything goes wrong we are liable to start looking for a hidden camera.

One (totally unscientific, it should be noted) survey in 2004 found that just 23 per cent of people had been part of a prank at work. A similar exercise last year found that 60 per cent of those who did not play tricks avoided doing so because they were concerned about the gag backfiring. If that seems unduly cautious, consider the fate of poor old Glenn Howlett, a Canadian council worker who was sent a joke memo by colleagues that notified him that he had to present a major report in two weeks. Howlett, failing to notice the date, rushed back from a holiday to start work on it – and promptly suffered heart palpitations, went on full-pay leave as a result of stress, and eventually took early retirement. In our litigious age, it's not surprising if many people decide that the risks are simply too great.

So does the April fool live on at all?

Certainly. In place of the domestic japery that once brightened up the first of the month is a cheerful new tradition of media pranks, which stand every chance of success thanks to the supposed authority of the perpetrators. In this format, astonishingly convoluted stunts, which may be the results of significant amounts of work by a large team of people, are perpetrated every year; every now and then, one of them enters our modern April Fool's folklore.

How did this new tradition begin?

The first great April fool of the media age, arguably not beaten to this day, came from the unlikely source of the BBC's documentary strand Panorama. In a magnificent 1957 jape that drew much of its power from the fact that no one would have believed that such an august programme would stoop so low, it reported on Switzerland's spaghetti farmers, who tended long, thin fields of the pasta-based crop. "Many of you, I am sure, will have seen pictures of the vast spaghetti plantations in the Po valley," the voiceover intoned, before adding that this year had seen a record crop thanks to "the virtual disappearance of the spaghetti weevil". The item provoked an avalanche of letters.

Have there been similar tricks since?

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These days, it's hard to get through a newspaper on 1 April without encountering one. And while it's hard for any to have quite such an impact as that first effort, the media-savvy public are still occasionally duped. Our friends at The Guardian scored a notable hit with its 1977 effort – a special report on the republic of San Serriffe, an Indian Ocean nation that consisted of the islands of Upper and Lower Caisse, with the capital of Bodoni – while this newspaper's finest hour arguably came in 1990, when a report claimed that the Mona Lisa's smile had been revealed by a careful cleaning process as a later overpainting hiding the original picture's sulking frown.

These days the most elaborate hoaxes tend to be perpetrated by corporations, which see in them priceless publicity potential. The modern standard-bearer is surely Google, which has in recent years unveiled a pigeon-based search algorithm, a research centre on the moon, and a broadband system that runs through the toilet.

What does the future hold for the tradition?

Despite its enduring popularity, April Fool's Day is under threat. The Health and Safety Executive, acting on a stream of complaints, has ordered an investigation into the potential risks of practical jokes in the workplace, with particular regard to 1 April. And MP Jo Kerr has tabled a motion calling for "this vile and outdated practice to be outlawed at once", and demanding that schoolchildren be issued with special "I ain't no fool!" headbands to ward off potential perpetrators. Still, fans of the form should not be too worried. As long as there are people gullible enough to believe anything they read, it seems unlikely the April Fool will entirely disappear.

Is it still funny to play tricks on April Fool's Day?

Yes...

* The attention paid to April Fool's Day by the media is proof that we all enjoy being taken for a ride

* These are troubled times. It's good to have a day when a bit of anarchic fun is officially sanctioned

* A bucket of water atop the boss's door will surely amuse even the most po-faced colleague

No...

* It's depressing that the most widespread version of the tradition now takes the form of glorified adverts

* Many people will think it inappropriate to be messing about in a time of global crisis

* It might be a bit of fun to you, but one person's joke is another's cruel jibe, and the line is very fine indeed