Today is the 1st of April and just like in many countries around the world, it's the day of jokes, hoaxes and pranks. Newspapers and other media publish fake stories but the real speciality in France is the Poisson d'avril. This consists of sticking a paper fish on someone's back and seeing how long they go without realising it. Once the fish is discovered you shout "Poisson d'avril"! Children adore trying to catch out their teachers if it falls on a school day or their parents when it's a day at home. My elder son has been sporting a fine specimen for a couple of hours as I write this, stuck on his back by his little brother completely unbeknownst to him.
Accounts vary as to the origins of the jokes and the fish connection. The theory with the most credence is that it arose out of a change in the calendar in the 1560s when King Charles IX ruled that the year would, from then onwards, begin on the 1st of January not the end of March as had been the case.