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Saturday, February 23, 2008

Leaping Leap Years

I think we can all agree that there are 365 days in a year, except for those years evenly divisible by four, which have 366 days: unless that year can also be evenly divided by 100, in which case they have 365 days again; unless they can also be evenly divided by 400, in which case they still have 366 days. The key to this convoluted system of leap years is Christopher Schlussel, better known by his adopted name Christoph Clavius, and that is actually a little linguistic humor since the German word for key is a “schlussel”, while in Latin a key is called a “clavius”. Ah, German jokes are so much better when told in Latin, aren’t they? “Duo flaccus homo abbulo accedo caupona”. But if you think figuring leap years are complicated you can thank your lucky stars that we no longer use the Roman calendar, because those people would have made the French seem logical.
See, the Roman calendar was based on the phases of the moon with a 19 year cycle because…it’s not important, trust me. Their calendar began with ab urbe condita, or the founding of the city of Rome (our 753 B.C.) and began with the year “1” because the “0” had not yet been invented. Their year was 355 days long and had just ten regular months - Martius, Aprilis, Maius, Iunius, Quintilis, Sexitilis, September, October, November and December - but they didn’t begin their year with the first of Martius because they didn’t have a first of anything. The Romans only had three actual dates every month – the kalendae (the new moon), two Nodes (the waxing and the waning moon) and the Ides (the full moon). This is why Julius Caesar was warned to ‘beware the Ideas of March’, because a full moon allowed plenty of light for all that conspiratorial running around in the dark. Individual days each month were only noted as so many days before the kalendae (or whatever) of the month. This is how you keep your calendar if your checks have to be dated the X-V-I of Quintlis. (And, yes, the word calendar came from the word kalendae.).
But the primary drawback to the old Roman calendar was that to make it all come out right every year they had to insert an 11th month, Mensis Intercalaris, right after Martius. But whether it was 23 or 24 days long depended on certain mystical astronomical calculations regulated by the “Pontifex Maximus”, who was an elected official. It was as if George Bush had ten months left in office but how many days were in each month was to be determined by Florida election officials. And since Julius Caesar was the Pontifex Maximus in 44 BC, he might still be in office today if the special senate select committee on term limits hadn’t stabbed him to death. But before he was term limited out, Julius had ordered a fix to the old calendar. The new Julian calendar had 12 equal months. January was added at the end of the year, in the winter, when nobody would notice, and a leap year was introduced every four years.
But the Julian Calendar was still a little long – by over 9 days by the 100 years later, leading to confused robins and tax collectors, and big fights within the church about how to determine the start of a full moon and when Easter was and what day of the week Easter was on, etc., etc. And that was why Ugo Boncompagni, aka Pope Gregory XIII, was thrilled when he was handed a rather obscure volume entitled “Compendium of the New Plan for the Restitution of the Calendar”, which was written by a doctor and math nerd named Luigi Giglio, whose non deplume was Aloysius Lilius.
Just a quick note about poor old Ugo Boncompagni; this guy was the George Bush of Popes. Everything he touched blew up in his face. He encouraged the King of Spain to build the Armada, and offered him a bonus for the first Catholic soldier to land in England. Needless to say, Phillip never collected. Ugo expanded the inquisition, determined to reconvert all those Lutherans in Switzerland by force, and thus brought an end to the Catholic Holy Roman Empire. Nobody has even tried to invade Switzerland since, not even Hitler. And Ugo was probably the last Pope to die flat broke. He did more through sheer incompetence to destroy the power of the church than did Luther and Calvin together. In fact, about the only thing poor old Ugo did right was to recognize the genius in Luigi Giglio.
Unfortunately Luigi had died 6 years before Ugo read his book, so Ugo turned the book over to his favorite Catholic overachievers, the Jesuits, and asked their best mathematical brain, Christopher Clavius, to check Luigi’s math. And Christopher knew the Catholic world needed three things; to lock in the date of the spring equinox as March 21st or 22nd, because that would keep Easter anchored securely in the spring; solve the problem of the wandering seasons, and please bring sanity to the length of the year. Not unexpectedly, the mathematician Clavius and his team of mathematicians saw the whole thing as a giant math problem.
What the Jesuits couldn’t know, because they didn’t have a decent atomic clock, is that a year is actually longer than 365 days by 11 minutes and 14 seconds - approximately. Now the simplest thing would have been to ignore those extra minutes, and let them pile up for 128 years until they equaled a complete 366th day. But Clavius didn’t even have the luxury of knowing that the earth revolves around the sun, because he hadn’t accepted that idea just yet. But he had invented the decimal point, and he did encourage the use of the “0”, which made his intricate calculations much easier. And he confirmed Luigi's numbers, which boiled down to was this; thirty days hath September, April, June and November. All the rest have thirty-one, except February, which has 28, except in a leap year when it has 29. See how simple that is?
So thanks to Luigi Giglio, Christopher Schlussel and poor old Ugo Boncompagni we now have a calendar that repeats every 400 years, February 29, 2008 and February 29, 2408 are both Fridays, and our calendar is good for the next 3,000 years. But there is a minor hick up in this magnificent system. It was recently discovered that the year 4000 ought not to be a leap year. Panic should follow shortly.
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