Time flies, they say, but the development of the calendar we use to measure the passage of it took centuries to perfect, as David Ewing Duncan documents. In addition to math and astronomy, Duncan shows, the Gregorian calendar we use today is equally the result of a quirky interplay of politics, history and religion.
Before the Julian calendar was introduced, for example, priests in the Roman Empire exploited the calendar for political ends, inserting days and even months into the calendar to keep the politicians they favored in office. Tired of the chaos that this undependable system eventually gave rise to, Julius Caesar finally set out to put the long-abused calendar back on track in 45 B.C., with a calendar that identified the length of the year as being 365 and the fourth part of a day long.
This was admirably close to the actual length of the year, as it turns out, but the Julian calendar was not so perfect that it didn't slowly shift off track over the following centuries. But, hundreds of years later, monks were the only ones with any free time for scholarly pursuits -- and they were discouraged from thinking about the matter of "secular time" for any reason beyond figuring out when to observe Easter. In the Middle Ages, the study of the measure of time was first viewed as prying too deeply into God's own affairs -- and later thought of as a lowly, mechanical study, unworthy of serious contemplation.
As a result, it wasn't until 1582, by which time Caesar's calendar had drifted a full 10 days off course, that Pope Gregory finally reformed the Julian calendar. Ironically, by the time the Catholic church buckled under the weight of the scientific reasoning that pointed out the error, it had lost much of its power to implement the fix. Protestant tract writers responded to Gregory's calendar by calling him the "Roman Antichrist" and claiming that its real purpose was to keep true Christians from worshiping on the correct days. The "new" calendar, as we know it today, was not adopted uniformly across Europe until well into the 18th century.
There are plenty of the sort of fun facts one would hope for in a book of this sort, and Duncan does his best to make the frequently dry subject matter sexy wherever he can (such as when he refers to the Julian calendar as "born of Caesar's tryst with Cleopatra"). Duncan gives credit to a number of lonely scholars who died in obscurity, but he often neglects to show how these men did their mysterious work. Preferring to address the politics of the day, he chooses not to explain, even in laymen's terms, how Copernicus used his astrolabe or Galileo used his telescope to figure out the nature of things.
This book would've benefited from an introduction, or a chapter somewhere, spelling out our current understanding of the "right answer" to the year problem, which stumped so many thinkers for so long. As it is, Duncan has written a book that colorfully illustrates the wild randomness of the calendar's creation and how it has shaped peoples' lives, but that chooses to leave the actual motion of the heavens in the dark.