Monday 1st April is April Fool’s Day. In France, prior to the year 1582, the New Year was celebrated for eight days, starting with the 25th of March, with the festivities culminating on April 1st.
With the reform of the Christian calendar under King Charles IX, through the influence of Pope Gregory, the Gregorian calendar was introduced, and New Years Day was moved to the first of January. However, due to lack of communications in those days, many people did not receive the news for several years. Furthermore, some obstinate individuals refused to accept the new calendar and continued to celebrate the New Year on April 1st.
These people were classified as “fools” by the general public and were often subject to some ridicule and were invited to bogus parties; hence, the tradition of April Fool’s Day.
Apparently, a popular prank throughout the 18th/19th Centuries, involved inviting folks to watch the fictional ceremony of washing the lions, said to take place annually on 1st April. Initially the ceremony was purported to take place in the moat area, but later versions involved sending prank victims to the non-existent white gate! The image above shows an admission ticket (from the British Museum) for a hoax 'Washing of the Lions' event supposedly taking place at the Tower of London on Wednesday 1st April, 1857. This image is in the public domain because it predates the Copyright Act of 1956.
As well as being April Fool’s Day, 1st April was also the joint celebration of Veneralia & Fortuna Virilis in Ancient Rome. Both festivals appear vaguely connected with Venus, whose advice was sought on matters of love and who was honoured on this day.