Linz’s Favorite Son

Or at least one of them, is Johannes Kepler. Like Linz’s least favorite son, Kepler wasn’t actually from there. Rather, he was born in Germany. Still he lived in Linz for quite some time, teaching mathematics and adding to his famous laws of planetary motion. Kepler did a lot in Linz, but the thing that captured my attention while I was reading about his exploits there this week was his participation in a debate about the adoption of the Gregorian Calendar.

Yeah sure Joe, sounds real interesting…click! Fine, but I’ve always found the topic fascinating — for what it says about the action of the solar system, but mostly for what it says about the all-too-common inaction of manmade political and religious organizations. For the Gregorian Calendar was officially instituted in 1582, but it took almost 500 years before it was finally, fully implemented around the world. And even today there are some holdouts.

But first, what exactly is the Gregorian Calendar? Well as the name suggests it’s a calendar that was instituted by Pope Gregory the XIII as a correction to the old Julian Calendar instituted by Julius Caesar in 46 B.C.. That calendar was based on a year (which is to say, the time between the Vernal Equinoxes) that was 365.25 days long. Pretty precise — save for the fact that the actual amount of time it takes for the Earth to complete one revolution around the sun is 365.24219 days. Doesn’t sound like much of a difference, but over time the discrepancy adds up.

It did by 325 A.D., by which time the leadership of the Catholic Church had begun to notice that different branches of the Church were celebrating Easter (the Church’s central feast) on different days. The reason: because all their various calendars were based on the cycles of the moon, not the rules of Julius Caesar. It was in that year, at the Council of Nicea, that a standard lunar calendar was introduced to keep all the members of the Church on the same page, liturgically speaking.

But that still didn’t solve the underlying problem, which was that time as measured by the Julian Calendar and time as measured by the actual movements of the moon and sun were still diverging. The Church’s lunar calendar had a built-in error of one day every 310 years. Which meant that by the mid-1500’s the Church’s calendar was out of phase with the regular Julian Calendar by four days. So Church time was out of phase with common time, common time was out of phase with the sun…everything was all mixed up.

At the Council of Trent in 1563 the Church approved a grand plan to fix everything. Fundamentally, the plan proposed to dump the lunar calendar and base liturgical (and common) time primarily upon the sun. The key to the whole thing of course was to figure out exactly how long it took from one Vernal Equinox to the next. Church astronomers settled on 365.2425 days. It wasn’t entirely precise, but it was close enough for jaz— er,…Gregorian chanting. Among the benefits of the new system, there’d be a leap year only once every 400 years instead of once every 100 years.

But getting everybody on the same system involved a somewhat jarring correction. Specifically, that the day after Thursday, October 4th, 1582 suddenly became Friday, October 15th, 1582. Or so said the Pope. That went down fine in places where the church held political authority (like the Papal States in Italy), but not so much in other locales around Europe. Thus Kepler’s debate with the city fathers of Linz some 30 years later on the relative merits of the Gregorian calendar. Do we do this crazy thing or don’t we?

Sure this seems like an esoteric subject for a pastry blog. But me, I wonder what it must have been like to live in Europe around the year 1600, where, depending on where you traveled, it could either be June 10th or June 20th depending on how the locals felt about the authority of the Pope. Just ask anyone I work with, I have enough trouble with time zones.

Spain, Portugal and the Polish-Lithuanian Commonwealth changed their calendars on time. And while the Habsburgs did their best to impose the Gregorian Calendar around their empire, Protestant holdouts in various spots resisted — for decades. Most of northern Europe came around by 1700 (Sweden held out until 1740). Britain gave in around 1752. Russia and Greece resisted the conversion the longest, even longer than Japan, which accepted the Gregorian calendar in 1873. They held out until 1917 and 1923 respectively.

Today the Gregorian Calendar remains the standard measure of time around the world. And while there are no official state holdouts, there are several religious ones. Specifically the Orthodox Christian churches. They celebrate Christmas just like the rest of the (Christian) world on December 25th, but do so according to the Julian Calendar, which is January 7th to us.