Continuing my obsession with the calendar, there are some even stranger stories which need to be told.
Most people know about the fact that the Julian Calendar will slowly drift by one day every 128 years. This posed a problem for someone like Pope Gregory XIII; so he was able to convince the Catholic church to change its calendar to his eponymous system which is the one we currently use.
Add a leap day as February 29 on years that are divisible by four (like 2016)
Unless they are also divisible by 100 (like 1800 or 1900).
Unless unless they are also divisible by 400 (like 2000).
Hence the reason why 1900 didn't have a February 29 but why 2000 did.
This was all very nice until you realise that some countries like England who were not very Catholicy at all (owing to Henry VIII who was cranky all the time) and the countries who had Eastern Orthodox churches also didn't like the pope, all told Pope Gregory XIII in no uncertain terms that he was wrong.
Eventually though, these countries did fall into line; with England finally doing so in 1752, Russia in 1918 and Greece being the last in 1923.
In the case of England. New Year's Day used to be April 25 which was Lady Day, or rather the Feast of the Annunciation of the Virgin Mary. In 1752, the calendar was punted forward by 11 days and the Wednesday 2nd September 1752 would be followed by Thursday 14th September 1752.
One remaining vestige of this is that the tax year in the UK which used to begin and end on April 25, was also punted forward by 11 days to April 6.
Sweden who was still using the Julian Calendar and who was in the middle of a 21 year war called the "Great Northern War" with Russia, added two leap days in 1712 and thus the year 1712 in Sweden had both a 29th and a 30th of February.
Sweden would adopt the Gregorian Calendar in 1753, when the 16th of February was followed by 1st March.
Russia on the other hand was still happily using the Julian Calendar right through the First World War. After it did finally adopt the Gregorian Calendar in 1918, the first day in February 1918 was February 14th.
This caused its own silliness, with the October Revolution of 1917 which had begun on October 25, now being celebrated on November 7th.
One of the days which I found that didn't fit into anything described here is what the Chinese Government politely refers to as the political turmoil between the Spring and Summer of 1989. This event is more commonly known as the June Fourth Incident or more bluntly as the Tiananmen Square Massacre.
I have seen this referred to as the May 35th incident as a way of subverting internet censorship in China.
One of the accounting programs that I use does better than all of these. It uses 40 days in every month and 15 months in the year. Those extra days and months are there for you to throw through journal entries without upsetting individual months.
They are labelled Undecimber, Duodecember, Trescember which are confusingly named because they are the 13th, 14th and 15th months. The 37th of Trescember (37-15-2016) isn't a normal date for most people but in the accounting world, it's allowed.