Transcript: By the late 16th Century, the Julian calendar was out of sync with the seasons. With an average length of 365.25 days, it is in fact a hundredth of a day longer than a true solar year.  After centuries, these hundredths of a day had added up to days, and the solar calendar was in fact ten days off.  Pope Gregory, representing the Catholic Church, instituted a calendar reform, adding essentially one rule to the Julian calendar: that you would skip the leap year in century years unless divisible by 400. With this extra rule the calendar will now very closely approximate the Solar year, and this calendar will be good enough for us to use for thousands of years to come.  Non-Catholic countries, the Protestant countries of England and America in particular, did not adopt the Catholic calendar for another hundred years, by which time their calendars were eleven days off.  Essentially, in one swoop, the governments of the United States and Britain lost eleven days going directly one year from April eleventh to April first.  Benjamin Franklin wrote in Poor Richard's Almanac to reassure people about the loss of the eleven days.  The French, a Catholic country, decided to mock the Americans by creating April Fool's Day to mark the day that the British and the Americans finally adopted the Gregorian calendar.  Have calendars never been sensible or rational?  At the time of the French Revolution, for twelve years the French instituted a decimal calendar with twelve thirty-day months, not named after Pagan gods, five festival days, a leap year, a week divided into ten days, the day into ten hours, each hour into a hundred minutes and each minute a hundred seconds, the world's only decimal calendar.  But because no other culture would follow this calendar, it was dropped by Napoleon after only 12 years.