Mapping Time : The Calendar

This fascinating book fully addresses a topic of much general interest by drawing together a wealth of diverse material on the much-trusted (and rarely disputed) phenomenon we know as the calendar. From the fundamentals of astronomy to the world's ancient time-keeping schemes, from the development of the modern-day calendar to the precise calculation of what happens when (as in, how does one arrive at the date for Easter Sunday?), this is a skillful yet approachable discussion of the calendar from both the historical and contemporary perspectives. Readers will even learn how to perform experiments and calculations for themselves by using such basic techniques as stargazing and simple mathematics.

The approach of the millennium has generated a spate of books on the history of our calendar. Here's an especially good one. According to Richards, the calendar originated in humanitys desire to track the natural phenomena on which life in primiti ve society depended. Seasonal cycles of crop growth and animal migrations relate to the sun; tides relate to phases of the moon; and the cycle of dark and light caused by Earth's rotation makes itself manifest every day. But the relationships among these three astronomical phenomena cannot be expressed simply. Much of the history of calendars has to do with compromises made in trying to juxtapose these three cycles. At the same time, in almost every culture, the religious impulse has imposed its overlay o n the calendar. Days of the week (an arbitrary but convenient division of time) were given names related to ancient gods or to planets associated with them spiritually; each of the major religions boasts its own calendar, with its own succession of season s and holy days. After outlining the science of calendar-making, Richards describes many calendars used over the ages, including the Mayan and Aztec, and the French Revolution's attempt to divorce timekeeping from religion. The mathematics of calendars is given due attention, especially the calculation of the day of the week for past dates, and conversions between calendarse.g., from our Gregorian calendar to the Jewish or Mayan counterparts. A final section discusses problems caused in Western calendars by the shifting date of Easter, estimated by a complex formula, and a major bone of contention among the various denominations. Appendices provide useful astronomical constants, the names of the days of the week in sundry languages, the French Revolutiona ry calendar, and a glossary of technical terms. Clearly written and filled with detail, this will be a strong contender in the calendar-book sweepstakes. (76 illustrations) -- Copyright ©1998, Kirkus Associates, LP. All rights reserved.

Both of these books are devoted to the question of how the world came to agree on what day it was. Both are written for a general audience although Richards is an academic, and his book is the more scholarly. Richards also has a more global perspective, whereas Duncan focuses on the calendar in the West.
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