Books: Calendar

I remember learning, as a child, how the date of Easter was determined each year: the first Sunday after the first full moon after the vernal equinox. Besides being complicated (compared to Christmas, or even Thanksgiving, which just required counting Thursdays in November), it seemed foolish to make the holiday move around so much every year. I couldn’t imagine why they – whoever “they” were – had decided on that formula.

And apparently not everyone could even agree on that, as our calendar always showed a separate date for the “Orthodox Easter.” I didn’t know anyone who was Orthodox, but presumably there were such people around, since the date was included on the calendar (our calendar didn’t include foreign holidays, as some calendars do).

Eventually, in some history class or other, I must have learned about the Gregorian calendar, but it wasn’t an important enough topic to spend much time on. I knew that different civilizations had used different calendars (in a class on the Middle Ages we learned about the rise of Islam, with their calendardated to Muhammed’s Hegira in our year 622 A.D., and I also knew that the Jews had their New Year in September), but I had little idea how we had come to have the one we do.

Several years ago I read Waiting for the Weekend (a fascinating book, as is everything I have read by Witold Rybczynski), which is primarily about the development of the two-day weekend and attitudes toward work and leisure. Rybczynski starts, however, by looking at the origins of the seven-day week, which was far from universal in the ancient world. That whetted my appetite to learn more about the origins and development of the calendar we live by today.

I purchased Calendar: Humanity’s Epic Struggle to Determine a True and Accurate Year several years ago, but found that it wasn’t nearly as quick and easy a read as Rybczynski’s books. David Duncan tells some fascinating stories about people who influenced our understanding of time, even if their influence on our calendar was very indirect. He puts them in their historical and cultural context, so he spends a lot of time (possibly the majority of it) on background information and going off on tangents.

Generally I like that kind of history-telling, because I like knowing the background and I like seeing things from an unusual perspective. But it makes for slow going through the book, because it takes so long to get from one major point to the next. Sometimes there was just too much detail, too much going off on tangents. By the time he got back on track of the main idea, I’d forgotten where he had been on the track when he had left it.

Along the way, though, I learned a lot of things I had not known before. I had no idea, for instance, that the system of numbering years from the (supposed) date of Jesus’ birth (today scholars date his birth at about 4-6 B.C.) did not come into use until over five centuries later. And it took another five centuries before it was widely used across Europe. Oddly enough, the system used previously numbered years from the beginning of the reign of Emperor Diocletian, who was responsible for a great persecution of Christians. By counting years in this manner, however, it was felt that this gave right veneration to those martyrs, and the idea of the new way of numbering years met with resistance.

I also was surprised to learn how great a role religion played, both as an impetus to get the calendar right, and to maintain existing calendars rather than changing them. (These two motivations worked against each other for centuries.) I can understand wanting the calendar to be right because a calendar year is intended to match the actual year in nature. I have a much harder time understanding the felt need to celebrate religious holidays on the “right” day.

Perhaps that has to do with growing up in a home where the whole idea of special days was scorned by my mother. She saw no reason why one day should be given prominence over others just because it happened to be exactly X years since some event (birth, wedding, or whatever). I thought it was silly of her to refuse to join in what I considered a harmless – and fun – celebration. (She seemed incapable of doing anything just “for fun” – everything had to provide some benefit to others or to one’s own personal growth.) But I suppose I absorbed her view that no day had any real significance beyond what I chose to give it.

Or maybe that’s simply the modern view, that meaning is what humans impose on our experiences, rather than something that arises from nature. In any case, it strikes me as very odd that people in medieval times worried that saints might not hear their prayers if they prayed by mistake on the wrong day. I question whether Christians in Heaven can hear the prayers of people on Earth to begin with, but even if they can, why would they care whether it was the day people on Earth had designated as that saint’s “day”? (These days, by the way, commemorated not the saints’ birth but their death by martyrdom.)

More than the saints’ days, however, what really worried Christians of that era was whether they celebrated Easter on the correct day, as it was the most important holy day of the year. During the first centuries after the Resurrection, various groups of Christians used differing methods of computing this date. Constantine wanted to consolidate both political and religious authority, and getting the bishops to agree on how to determine the date of Easter was one part of his plan to accomplish this.

But even after the Council of Nicaea came up with the formula used today, and determined that March 21 was the vernal equinox, this did not solve the problem. The calendar then in use, the Julian calendar named for Julius Caesar who had established it, assumed the year to be 365.25 days. That’s only about 11 minutes longer than the true year, but over the centuries those minutes add up to days. Eventually the gap became large enough that even people untrained in math or astronomy could tell that the vernal equinox according to the calendar was most certainly not the day when day and night were of equal length.

Knowing there was a problem, and finding an acceptable solution, were two very different matters however. Partly it was lack of adequate measuring tools. Even aside from mistaken notions about a geocentric universe, people didn’t have a mathematical system capable of expressing (much less calculating) small fractions of a day. A positional number system (such as ours, with “places” for ones, tens, hundreds, etc.), the concept of zero, and the decimal point for expressing fractional parts – these developed in other cultures and gradually spread westward to Europe. In a culture where most people were too busy surviving to spend much time learning (and books and educated teachers were correspondingly scarce), such knowledge spread slowly.

Even when such knowledge was available, however, learning meant change and change challenged tradition, which in medieval Europe meant challenging the Catholic Church. I don’t know whether Duncan is as “antichristian” as one reader comment on amazon.com complains, but he makes it clear that for centuries much of the resistance to calendar reform was based on the idea that time belonged to God and it would be arrogant of man to try to know too much about it. I know that in some ways the “Dark Ages” were not as dark as they are often made out to be, but I have little trouble believing that religious conviction seriously hindered development of knowledge that was (wrongly) believed to be opposed to piety.

Even once learning began to take higher priority and the Catholic Church lost its absolute authority, there were other challenges. In the mid-fourteenth century, a calendar reform had actually been planned, but it never took place because mere survival took precedence over such intellectual concerns. The bubonic plague wiped out an estimated third of the continent’s population, and even after people stopped dying from the plague, the economy and political situation had been so devastated that it took a century to recover.

Once Europe did recover, the increased trade not only within Europe but with other regions of the world made an accurate calendar even more important. (How do you calculate interest payments unless you know how many days have gone by? How do you know whether a shipment arrived on time if you don’t agree on what day it is?) But at the same time that this made calendar reform more important, it made it more difficult to enact because it required coordination among so many different groups of people.

Then there was the Protestant vs Catholic issue. The Catholic Church was the closest Europe had to a universal authority, to impose such a sweeping reform that would affect nearly everyone’s life to some extent. But Protestants who viewed the Pope as Antichrist were hardly going to accept a calendar promulgated by him. To them it was a matter of defending the true faith once delivered to the saints, to refuse to alter the calendar that had been in use since the time of Christ.

Eventually just about everyone finally did make the change, just to stop having to deal with two calendars (Old Style and New Style). But because different countries made the change at different times, comparing dates from any time during the transition can be confusing unless you keep close track of whether a date is given Old Style or New Style. Some countries didn’t even start the year on January 1 under the old system, so an Old Style date in one country could correspond to not just a different date but a different year in another country. And while the countries that made the change first only dropped ten days from their calendar, countries that made the change much later had to subtract eleven or more days.

One last note, on a topic that I hadn’t understood when I encountered it previously (I forget where) – now I finally understand what the “precession of the equinoxes” is about. There are two ways to measure the year from natural phenomena, either based on the seasons (the “tropical” year) or the earth’s position in space relative to the sun and stars (the “sidereal” year). The former measures the time from one spring equinox to the next (or autumnal equinox, or the summer or winter solstice – each of which gives a very slightly different measurement, for reasons I don’t quite understand); the latter measures the time from when the earth is in a particular position in space until it gets back there after traveling once around the sun.

These two “years” are almost the same length – but not quite. There is about a twenty minute difference between the two. (I can recognize a few constellations and I know that they appear differently in the sky depending on the season, but I can’t imagine paying close enough attention to notice that twenty-minute difference between the two types of years. I was surprised to learn that it was recognized in ancient Alexandria, even though the exact length of the year was unknown.) If there were a way to mark a particular point in space, one would find that, over many many centuries, the earth would reach that point earlier (or is it later? – I still have trouble with this part) in the year as measured by the seasons – even with an accurate calendar.

Next maybe I’ll try to read another book I bought a few years ago, about how cathedrals were constructed to serve, in part, as solar observatories to assist in all this calendar calculation. But I think I’ll look for some other, easier read first…

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2 Responses to Books: Calendar

  1. Peter L says:

    Re:Date of Easter– Actually, it would make the most sense to have Easter coincide with the corresponding day of Passover on the Hebrew calendar. The only thing with that would be that it would not always be on a Sunday. But as Christians, should it matter when we celebrate the actual resurrection of the Lord Jesus? Is not the reason we worship on Sunday because we are celebrating it every week?

  2. Karen O says:

    Very interesting.

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