Marking Time: The Epic Quest to Invent the Perfect Calendar

This is not only the best book on measuring time and calendars, this is one of the best factual books I have ever read on any subject whatsoever. Almost every page in this meticulously researched book brims with fascinating information! Steel introduces words rarely used and shows why they're needed, gives background settings in history, politics, religion, and, of course, astronomy. Steel is an astronomer, but from reading this book one feels in the presence of a true polymath.The very first chapter drew me in with that formula, by asking what day is George Washington's birthday. February 22nd, 1732, right? Not exactly! Not only does Steel take us into the "missing 11 days" of Julian/Gregorian year change, but then shows how New Year's Day has changed as well. It wasn't always January 1st, in fact the year changed on March 25th. The more you read, the more there is behind each new fact. This is James Burke's _Connections_ on steroids! (George Washington always considered February 11th, 1731 his birthday, if you were wondering. Except then we have to talk about double-dating; he was born on Feb 11th 1731/32!)Some of Steel's asides had me laughing uproariously; what could have been a ploddingly dull and thick treatise absolutely sparkles. One of his best observations comes after painstakingly explaining how the Vatican came up with the Easter _computus_ (method of computing). After showing the historical claim that this method was "perpetual" he mentioned how long-term calendars will misalign as planetary rotations change, and computing Easter until the year 8000 was a mite ambitious. Then, he slyly mentioned that the Roman Catholic Church still presumes that Jesus is returning, so why would they need a perpetual Easter calendar, anyway?About the only defect in the book is the pervasive Christian viewpoint; not that Steel is religious. He isn't, and says so several times. But this book is a product of someone brought up in a Christian country complete with Established Church. More attention to other cultures' calendars would have been appreciated, especially after spending dozens of pages on secret plots involving rival Christian factions and their timekeeping ideas. I was surprised at how little mention was made of the Mayan calendar, for example; blink and you miss it.Despite this deficit, this book is otherwise absolutely terrific. It's not a book to plow through in an airport, though. It is a book to savor, for each new turn calls back so many associations made earlier. When I finally finished it, I felt the need to go back to Chapter 1 and see how much I remembered...what was that Sothic year again? Who was the Metonic cycle named for? What the heck is a nutation? This is a book that never speaks down to its audience; Steel assumes you are an intelligent reader and enjoys learning as much as he does. Enjoy!

This is a comprehensive and flowing account of the development of the world's adopted calendar. It is, by far, the best book I've read on the subject of time keeping. The so-called 'best sellers' that everyone seems to have read can't hold a candle to the breadth of experience contained here. Steel's style may be a bit too chatty for some and too full of anecdotes about his youth in England and his experiences in the US and Austrialia. But then the author is a seriously good astronomer and this topic involves some pretty lateral concepts. He keeps you on board by making it fun and there's a detailed appendix at the back where all the relevant astronomical details are introduced in an easy style .... just in case you aren't an astronomer. Marking Time's main aim is to explain why the Julian calendar was replaced. The modern calendar designed under Pope Gregory was built to reflect the length of time it takes the earth to pass between successive vernal equinoxes in March. Since the vernal year is almost constant, Pope Gregory's calendar is pretty accurate in tracking the time span between vernal equinoxes. The Julian version was a first approximation and therefore suffers from great inaccuracy over the centuries. There were calendar proposals made by others in the middle ages that were even more accurate. Why were they rejected? Steel tells you why.Steel also has an interesting religious-political theory for why the British finally adopted the calendar for it's empire in the mid-eighteenth century. It's all to do with the 77th meridian and Protestant England's fight against the Catholic church. I'd never read this stuff before - or his theory that universal time might be better measured from the US east coast - and was gripped. The freshness of his style is what made this book so memorable.Marking Time's other aim is explain why you can't build a calendar for all the ages. It simply isn't possible. The earth's orbit around the sun is slowing down. So what is accurate today clearly won't be in the future. The lunar orbit isn't constant either so a lunar based calendar won't solve your problem. In any case, a day is only 24 hours long on four occasions in a year and the year itself can be defined in more than one way depending on whether you're looking at the sun or the stars.After reading this book you'll realise there are a lot of very clever people in the world and also a lot of very silly laymen writing books on subjects they clearly don't understand. Duncan Steel isn't one of the silly people. You'll learn a lot from Marking Time that will fundamentally change the way you look at the world ........ and your watch.

With the year 2000 came quite a few books about the history of the calendar. I've read quite a few of them, and I can say that Daniel Steel's book is by far the most informative of them; it is also remarkably well written, especially considering the complexity of the problems surrounding the development of our calendar, which the author does not shy away from. I'll mention one issue here, because it was new to me: it is difficult to say exactly what a year is! More to the point, there are several different definitions of what a year is, and they have different lengths. The number you usually see quoted (365.2522 days) is the "mean tropical year". But you could instead measure the (mean) time between successive vernal equinoxes, and you get a slightly different number (365.2524 days). The author makes the case that the Gregorian calendar was designed to match this second definition (because the date of Easter is tied to the vernal equinox). This means that the Gregorian year (365.2425 days) is quite a bit more accurate than most people think, at least if you accept its intended goal.