You might get a ‘fish’ stuck on your back on April Fool’s Day – if you’re in France on 1 April, don’t be surprised if children try to stick paper fish to your back and call you a ‘Poisson d’Avril’ (April Fish). This tradition is supposed to have started in the 16th century when King Charles XIV of France changed the calendar and those who continued to celebrate the end of the New Year at the end of March were ridiculed as fools.