Mapping Time: The Calendar and Its History

nice, documented, interesting compilation/essay on the most important topics in the study of calendars. good place to start if you are interested in the topic. apparently started as the author wanted to build algorithms to program a computer to switch between dating systems. a few places i had to scratch my head and wonder about what he was saying, a bit more explanation in those contexts would have helped. the glossary in the back is a very good idea, i used it several dozen times. a bit more diagrams and hand holding would have improved the book for me. makes what could be a dull and boring subject, interesting, flowing and a worthwhile read. probably a bit advanced for the average person at places, but don't get discouraged, keep reading and struggling with the material.

This is a nice examination of the different calendars and methods of mapping time that humans have employed over the centuries. On the surface it has the air of a dusty reference book, but inside the author is often witty and amusing as he covers the histories and backgrounds of different dating systems. I'm especially impressed by his inclusion of the different algorithms used to calculate dates, of Easter for example, which are marvelously complex. Most readers will never have occasion to use these algorithms, but its nice to know they're there. I also appreciated the charts and the glossary of the more obscure calendrical terms.

Designing calendars is one of the more difficult tasks that human beings have set themselves. You first needed to -determine- the lengths of the cycles of the solar year and the lunar month. This was not an easy task, and it was not achieved until well into recorded history. The various cycles don't fit into each other particularly easily, either. With a solar year of just under 365.25 days, and a lunar month of just over 29.5 days, you aren't going to get it to come out even in the short run. You can stick with the sun and ignore the moon --- the solution of the Roman calendar fixed by Julius Cæsar. You can go with the moon, and leave the seasons to fall where they may --- as Muhammad, the desert-dwelling prophet of Islam, chose. Or you can try to keep the moon and sun tied together, necessarily loosely. This requires a number of cumbersome kludges, as the Babylonians, the Jews, the Chinese, and the Christians who fixed the date of Easter all discovered. These calendars took a lot more thought than the ones that simply discarded one or the other heavenly lights, and rank among the most intricate and intriguing works of ancient astronomy. This book contains a complete listing and description of the several solutions people have come up with to this seemingly intractable problem of arithmetic.

In this well-illustrated book, the author accurately presents lunar and solar calendars. A history of the Egyptian, Mayan, Chinese, Jewish, French Republican, Roman, prehistoric and present-day Gregorian calendars is provided. The author has also included commentaries about astronomy, writing, counting, the week, the month, the year and calendar reform. An excellent readable reference on a fascinating subject for the interested reader.