Marking Time

by Duncan Steel

Cover image

Publisher: John Wiley & Sons
Copyright: 2000
ISBN: 0-471-40421-7
Format: Trade paperback
Pages: 398

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It's hard to think of something more central to our daily lives and yet more strange and full of odd names and bizarre rules than the calendar and our time-keeping system in general. After reading this book, one realizes that there are also few areas as full of simplifications, misconceptions, and misunderstood history, and Steel takes a great deal of glee in pointing them out. Subtitled The Epic Quest to Invent the Perfect Calendar, this is roughly a history of the modern Western calendar, but it's full of digressions on weird aspects of timekeeping, the theory and purpose of calendar design, different dating systems, and even a fair bit of political conspiracy theory (but more on that in a moment).

Steel is an astronomer rather than a historian, although he's clearly done quite a bit of research for this book. His focus shows in attention to the implications of different time systems, the astronomical processes that they attempt to model, and the detailed mechanics and mathematics of the calculation of Easter (which was the primary motivating force behind the Gregorian calendar). One of the most interesting parts of this book for me was the clear explanation of just how complex the revolution of the Earth around the Sun is, the various different "years" that one can measure, the problems with connecting a lunar cycle with a solar cycle, and the long-term drift that will require that any calendar based on nature, no matter how well-designed, eventually be corrected. Sometimes this is a bit hard to follow (particularly in the appendices which lay out more of the detail), but Steel repeats the same material from different angles and usually hit on one that made sense to me on the second or third try. I think I understand precession of the equinoxes now, and some of the bits of trivia are wonderful. I expect some of them will be old hat to an informed reader, but possibly different ones for different readers; I already knew a lot about the origins and rationale of time zones, for instance, but had never realized that obviously the Earth rotates slightly faster than once per 24 hours since it's also revolving around the Sun and the day is based on the return of the Sun to the same place in the sky.

There's a surprising amount of background of this type required in order to understand the goals of a calendar and the possible methods for accomplishing those goals. As with so many of these topics, a modern sense of superiority over our ancestors evaporates when one realizes just how much they got right with far inferior calculation methods and just how complex the problem is. For instance, the Gregorian calendar is frequently criticized for being strange and inferior to other possible calendars, but while Steel does lay out one calendar that is better by most measures, Marking Time will give you an appreciation of just how good the Gregorian calendar is at its actual goal. It may drift somewhat from the tropical year (roughly, the average year based on all four solstices and equinoxes), but it keeps the year length close enough to the vernal equinox year as to not require correction for around 8,000 years. And stabilizing the vernal equinox, not the rest of the seasons, was the purpose, since the vernal equinox determines the date of Easter.

The history, on the other hand, is more scattered and less satisfactory than the math and astronomy. We're introduced to most of the major players and some of the social history, but Steel's ability to create a sense of story is hit and miss. He points out interesting factual errors in common understandings of the origin of the calendar (and opens one's eyes to just how chaotic the calendar has been at times in the past), but he also speculates frequently about motives and digresses into math more often than he needs to. The most interesting parts of the history also suffer the most: the dating of Easter and the switch from the Julian to the Gregorian calendar are complex topics that rightfully dominate much of the book, but he never convinced me of his theories about the motivations of British colonization. I suppose it's conceivable, given the religious feeling at the time, that the English really cared deeply about controlling "God's longitude" where the date of Easter would stay stable on a single day following the introduction of a proposed superior calendar no one actually used, but with a lack of supporting primary sources and much speculation in the book, I grew tired of having most major political events at the time connected back to this.

There are a few other flaws of focus, places where I think Steel missed an opportunity to write a more popular history. For instance, while there's a detailed discussion of the origin of seven-day weeks, the derivation of the names of the weekdays is dealt with only in passing and only in English. The origin of month names is told only in snippets and mentions here and there, and he never goes through the entire calendar. He also focuses almost exclusively on the western calendar except for one survey chapter, which means that one gets a belly full of Easter calculation methods and almost nothing about the Mayan or Chinese calendars.

Still, this is certainly more analysis, detailed history, and fascinating trivia about the calendar and about time-keeping in general gathered in one place than I've ever seen before, and I thoroughly enjoyed reading it. It takes a bit to get used to Steel's writing style — he discusses the structure of his own book in advance quite a bit more than is necessary — but he has an infectious enthusiasm for his topic and a good grasp of making the reader feel more intelligent than before. And if you want an exhaustive explanation of exactly how the date of Easter is calculated, with the rationale behind all the steps and a historical discussion of choice of date and system, you're not likely to find a better resource.

Rating: 7 out of 10

Reviewed: 2006-09-28

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