Friday, January 20, 2012

The Politics of Calendar Reform

Posted by Darin Hayton on 01/20 at 10:53 AM

Whether we are reforming a calendar or adjusting a the seconds of the day, time and dates are never neutral. They have always been laden with political and religious significance. Consequently, any effort to adjust or change the ways we calculate both the time and the date quickly become embroiled in competing interests.1

Article from the NY Times on the leap second

The recent press coverage on “leap seconds” and whether or not should continue to insert a leap second as needed recalls a the debates 500 years ago about correcting the calendar. Then, as now, the problem was correlating the social calendar to the perceived astronomical motions. The errors they were seeking to rectify were not, however, on the scale of seconds but on the scale of days. And they weren’t trying to correlate the earth’s rotation to the time of day, but the annual revolution of the planets around the earth to the day of the year. But the basic issues remain the same: How do we keep the calendar humans use to structure their daily lives in sync with observed astronomical phenomena.

In 1514 Pope Leo X summoned to Rome a body of experts, headed by the interminable Paul of Middleburg.  Leo charged them with proposing solutions to rectify the calendar. At issue was no less than determining the correct date of Easter and correlating it with the spring equinox. Astronomers and astrologers, and most anybody who cared, knew that the planets took a little more than a year to return to the same place in the sky. As a result, the spring equinox drifted through the calendar, becoming slightly later each year.2 Leo X was not the first pope and Paul of Middleburg not the first astrologer to confront this problem. Among others, that most famous fifteenth-century astrologer Regiomontanus also tried to tackle the problem. And a 150 years earlier, the Byzantine astrologer and polymath Nikephoros Gregoras tried to persuade Emperor Andronikos II to correct the calendar. None of these efforts gained any traction.

In the 1510s, when Leo X confronted the problem, calendar reform seemed poised to succeed. In the autumn of 1514 the pope sent Paul of Middleburg’s suggested reforms to all the Christian princes and requested that they consult with their most learned astrologers and reply by the end of the year. Astrologers throughout Europe working for local princes, kings, and even the Holy Roman Emperor Maximilian I, quickly penned responses and critiques. Many of their replies no doubt have been lost while others lie unexamined in archives across Europe. Copernicus purportedly received a copy directly from Paul of Middleburg, but his reply, if he chased to write one, has not been identified.

Some replies were printed. When Emperor Maximilian I received the pope’s request, he turned immediately to his two best astrologers, Georg Tannstetter and Andreas Stiborius. Both Tannstetter and Stiborius had come to Vienna most likely at the emperor’s urging to teach at the University of Vienna and to provide astrological expertise to the imperial court. Maximilian asked them to evaluate and reply to Paul of Middleburg’s suggested reforms.

They set to work and produced a pamphlet outlining their position, which they initially dictated to their protégé Andreas Perlach. Perlach’s original manuscript copy still survives in the Österreichische Nationalbibliothek in Vienna and was a few weeks later printed as a pamphlet.

A manuscript copy of Stiborius and Tannstetter’s suggested calendar reforms (Source: Landesbibliothek Linz, cod. 170)

For the emperor, there was more at stake than simply correcting the calendar. It was a matter of national pride, the “glory and fame of our German nation” depended on their response:

We most eagerly entrust this to you so that when you receive this you, with exacting care for this enquiry, might apply yourself very carefully to it, and through your judgment and opinion you might increase and extend the glory and fame of our German nation.  At the very least, you will convey to us by the hand or our counselor and secretary Jacob de Bannisis a written account of your judgment and council regarding the Pope’s enquiry, if you will be unable to come to the aforementioned tenth session, on 1 December.3

Despite their best efforts, Tannstetter and Stiborius missed the 1 December deadline by two weeks.

The problems with the calendar, they claimed, arose from Church’s habitual use of mean planetary motions rather than the actual motions. They also accused the Church of sloppy calculations. They endorsed some of Paul of Middleburg’s suggestions while rejecting others as too complicated. They opted for a fixed date for the spring equinox, 8 March. They also suggested periodically omitting a day to keep the solar and lunar cycle from drifting out of sync, and they begrudgingly offered to calculate both the lunar and solar cycles for the next 1500 years so that people would know what to expect.

They were hopeful that finally the problems with the calendar would finally be corrected, thanks in large part to the availability of printed literature. They pointed out that in 1514 the proliferation of almanacs and wall calendars had helped to disseminate astronomical and astrological knowledge. They claimed that now even “moderately educated and indeed the uneducated, and almost children, are able to possess and read what a few centuries ago only the most learned would have been able to read”.4 Moreover, contemporary astronomical tables were more accurate than ever before.

Despite their enthusiasm, calendar reform had to wait another 70 years. Acting on the resolution from the Council of Trent, Pope Gregory XIII convened a group of experts and once again charged them with correcting the errors that continued to plague the calendar. By the end of the decade he solicited comments from astronomers and astrologers in various countries. By 1582 the pope issued the bull that established the calendar that remains in use for much of the western world today.

Adjusting the calendar in the 1580s was as problematic as it had been in 1514 and as it seems to be still today, with different countries arguing for different calendars. Initially only a handful of Catholic countries adopted the Gregorian Calendar on the date specified by the Papal Bull. Over the next few months more Catholic countries adopted the reformed calendar. Protestant countries rejected or simply ignored the new calendar, often seeing it as some kind of plot to re-subjugate them to Rome. Protestants in Bohemia rejected the new calendar as a Catholic-Habsburg form of oppression. Countries like Denmark and England didn’t adopt the Gregorian calendar until well into the 18th century. Russia didn’t adopt the new calendar until after the October Revolution in 1917.

It is no surprise, then, to read that the commission charged with deciding the fate of the leap second postponed making that decision until it can “ensure that all stakeholders have been adequately associated with a step which will clearly influence our future.”5

See Thony C.’s recent comments about BC/AD here.
1See, for example, the NY Times articles: “A Second Here a Second There May Just Be a Waste of Time” and “Decision About One Second Is Postponed for Three Years”.
2A year ago the precession and historical knowledge of precession garnered considerable attention in response to astronomers’ claims of a new zodiacal sign and subsequent attacks on astrology. See, for example, Rebekah Higgitt’s posts “Astrology is Rubbish”, but … and Should we debunk astologers more respectfully?, see Thony C.’s The astrology wars and abandoned scientific research programmes, and my own post What Exactly is Accomplished by Asserting “Astrology is Rubbish”? on the topic.
3Andreas Stiborius and Georg Tannstetter, Andreae Stiborii Boii theologi et mathmatici et Georgii Tannstetter Collimitii phisici et mathematici, super requisitione sanctissimi Leonis Papae .X. et Divi Maximiliani Imp. P. F. Aug. De Romani Calendarii correctione Consilium in Florentissimo studio Viennensi Austriae conscriptum & aeditum (Vienna:  Johannes Singrenium, [1514]), A1v.
4Ibid., B1v.
5ITU Radiocommunication Assembly defers decision to eliminate the leap second”.

Tags: andreas perlach, andreas stiborius, calendar reform, emperor maximilian i, georg tannstetter, gregorian calendar, leap second, paul of middleburg, pope gregory xiii, pope leo x


Comment posted by Thony C. on 01/20 at 11:54 AM

By a strange coincidence I am preparing a lecture on the calendar reform at the moment for the 29th February (the perfect date for it). Yesterday I actually read about Tannstetter’s and Stiborius’ answer to Paul of Middelburg. They will get a very brief passing nod in my lecture, which is centered around Clavius (he’s local you know). Will feature the Clavius Maestlin punch up.

Thanks for the links. Upon rereading I think my astrology wars post is actually quite good wink

Comment posted by Darin Hayton on 01/20 at 12:03 PM

I’m sorry to miss your lecture. I grow increasingly interested in Paul of Middleburg’s and Leo X’s efforts to reform the calendar. More specifically, I am intrigued by the responses. I’ve got a handful of ms. responses that I need to work through.

Yes, “The astrology wars” post was quite good. I borrowed some of your language about research programmes in a talk I gave to a room full of astronomers and phycists last spring. It worked really well. So thanks.

Comment posted by Thony C. on 01/20 at 12:19 PM

My reading was of course secondary literature. Would be interested in the results of your primary researches when they’re done. John North thinks Leo’s & Paul’s efforts were stymied by Leo having to go off and fight some wars. The point is interesting because the need to reform the calendar was known at least since Bede and I think all of the efforts were actually hampered by the Catholic political system.

The Pope is an elected absolute monarch so there is no continuity as in a hereditary monarchy and each new Pope has to start from scratch. On the other side the Popes are generally so old when elected that their reigns are usually relatively short. Result no time for a calendar reform.

There appears to have been some continuity of purpose in the 16th century starting with the efforts of Paul & Leo and culminating in Gregory’s reform. Somehow they kept the ball rolling long enough to get the job finished.

What do you think?

Comment posted by Darin Hayton on 01/20 at 01:16 PM

Certainly the pope had more immediate issues to worry about than the calendar, everything from domestic stability to solidifying authority across Christendom to arguing for one pope over another.

Given the way that religion, politics, and social control were bound up in the latter part of the 16th-century, I think the Church (not just a pope now, but the Church) probably saw the calendar as a useful tool to impose conformity. It was important enough to make it into the Council of Trent. In 1563, as I recall, the Council mandated that the calendar had to be reformed in stages. This was the first time a council had confronted the calendar since Nicea, 1200 years earlier and when the Church established a method all Christians should use to calculate Easter.*

The cynical side of me agrees with 16th-centuryt Protestants and sees the motivation to bring about calendar reform and the efforts to promulgate that reform: a papal ploy to reassert Roman/Papal authority.

But then, I can be cynical.

*This italicized text replaces an earlier, incorrect statement. Thanks to Thony C. for catching my error.

Comment posted by Thony C. on 01/20 at 01:57 PM

I think we must be equally cynical as I agree with you and the Protestants.

Comment posted by Thony C. on 01/20 at 02:00 PM

BTW Nicae did not set the date for the vernal equinox. All that was decided at Nicae was that all Christians should celebrate Easter on the same day. But which day and how to calculate it was left open. It wasn’t till about 1000 BCE that unity was finally achieved.

Comment posted by Darin Hayton on 01/20 at 02:03 PM

You’re right. My mistake about Nicea. Thanks for keeping me honest.

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