Happy All Fools' Day/Poisson d'avril

Origins: In 1564 the French king of the time, Charles IX, decided they were going to adopt the Gregorian calendar and that, in future, New Year's Day would be celebrated on 1st January - no longer would it be held at the start of spring. Now, like in any other society, there's always going to be a few who think "Oh, really?" and carry on in the old tradition - like the campaigners for the retention of imperial measurement who are still challenging the authorities' right to impose it - and France had more than a few. There were also others who never got to hear of the change officially and just carried on with the old tradition oblivious of what the king had said. It was these characters who resisted (or never knew about) the change and who carried on celebrating New Year's Day on 1st April who were laughed at and regarded as fools and to mark the occasion people started to send them foolish gifts and invitations to parties that were never going to happen. These victims, at the time, were called "poisson d'avril" or April fish and the reason for this is disputed. One suggestion is because at this time the sun is leaving the zodiacal sign of Pisces (the fish) the other is because in April the newly hatched fish are easy to catch.So the French started it and by the 18th century it was widespread in Britain and the various emigrants to the Americas introduced it over there. One of the more favourite pranks at the time was to send someone on a "fool's errand" by sending the unwary to fetch or collect something ridiculous - a joke that was frequently played on young apprentices on their first days at work, probably right up until the 1970s. Unwary engineering apprentices were often send to the stores to fetch "a hat full of nail holes" or to go for "a long weight [wait].