On 1 April, grown-ups around the world get to act like kids and pull pranks on their nearest and dearest.
Broadcasters have the public gobsmacked with unlikely headlines; parents are on edge waiting for foghorns to go off at the breakfast table; teachers are wary of any 'misplaced' whoopie cushions - the list goes on.
Regardless of whether you plan to take part, or you simply want to keep yourself from looking the fool, it's good to be prepared for this unusual day.
Where did it come from?
Fittingly, the origins of April Fools' Day are shrouded in mystery. While some believe that it was used as a way to celebrate the turn of the season, welcoming spring with joy and foolishness after the short and dark winter days, others think that it refers to the adoption of a new calendar in the Middle Ages.
Some historians speculate that the custom dates back to 1582, when France switched from the Julian calendar to the Gregorian calendar, meaning that the new year began around 1 April. Those who forgot that the start of the new year had moved to 1 January and continued to celebrate it in April became known as "April fools."
Some historians have linked the prank-filled day to festivals such as Hilaria (Latin for joyful), which was celebrated in ancient Rome at the end of March and saw people dressing up in disguises and mocking fellow citizens.
What historians generally can agree on is that the custom came to Britain during the 18th century, and there is evidence of a two-day event in Scotland called Huntigowk Day that saw people being sent on joke errands and having fake tails stuck to their backsides.
What type of pranks are pulled?
Whether you want to scare your sister with fake spiders, or welcome home your other half with a surprise water balloon fight, there are plenty of fun and safe ways to celebrate this silly day.
If, however, you want to take things a step further, take inspiration from these playful pranksters...
A broken antique
Flying penguins
Richard Branson's UFO
Spaghetti harvest
