Welcome to an extended February. It's a leap year, so there are five Sundays in February for the first time since 1976, and March is further away than normal. Good, that means I won't be getting older quite so quickly. I'm celebrating this 'leap month' by bringing you a daily dose of time-related trivia, investigating how our calendar came to be. Each time fact will be number-related, so I'm starting today with '0' and gradually increasing to reach '25800' by the end of the month. There'll be plenty of other non-time-related stuff too, as usual, but I'll start today with a very brief summary of how the calendar we use today has developed.
Man has attempted to map the seasons since prehistoric times. The phases of the moon provided the most obvious means of doing this, the period from one new moon to the next becoming one mo(o)nth. Unfortunately the time the moon takes to orbit the Earth isn't easily related to the time the Earth takes to orbit the sun. 12 lunar months make a year that's too short, but 13 are too long, so lunar calendars are doomed to inaccuracy. The Babylonians and Ancient Egyptians both spotted this problem and added whole extra months as required to try to keep in line with the rising of the stars and the flooding of the Nile.
Our calendar would be a simple matter if the Earth took exactly 365 days to orbit the Sun once. Unfortunately it takes a little longer than this, roughly (but not exactly) a quarter of a day extra. Miss out the quarter days and slowly, inexorably, the seasons don't match up with the calendar any more. Julius Caesar discovered a solution to this problem when he met Queen Cleopatra's chief astronomer during a bonking diplomatic visit to Egypt. Caesar introduced his Julian Calendar in 45BC, ending an age of chaos in which Roman years could be as long or as short as the priests decreed. He established 12 months of roughly equal length, and announced that February would have an extra day every four years. More on the Roman calendar here, here and here (and more details later in the month).
The Julian Calendar was good, but it wasn't perfect, so by the middle of the 16th century the seasons and the date of Easter were again in a right mess. Pope GregoryXIII was forced to remove 10 days from the year 1582 in order to allow the Earth to catch up with the calendar. He also announced that, in future, end-of-century years would no longer be leap years, except for years divisible by 400 which still would. The non-Catholic UK (and America) waited until 1752 to make this change, by which time an extra day had to be lost. Were it not for this calendar alteration then today's date would still be January 19th, not February 1st. Few people have changed our view of the world quite so fundamentally as Cleo, Jules and Greg.
Look before we Leap
