When you look at a clock or calendar, do you ever stop to think about the years of human effort that have gone into the science of telling time? Most people take clocks and calendars for granted—yet to understand them, one must know something of astonomy, geography and history. Psychology also plays a part.

Isaac Asimov has gathered his facts from many different fields of knowledge. In this revised and expanded edition, he presents a comprehensive story of time, describing the complications that can arise from such simple things as the earth’s rotation on its axis. He explains why the moon was the basis for the first year, why the lunar year doesn’t match the seasonsw and the problems mankind has faced in trying to make the phases of the moon come out evenly with planting and harvest time.

The numbering of years, naming of days of the week, vagaries of Easter, and calendar reform are but a few of the fascinating topics covered. Written in the same informal, entertaining style that has won acclaim for Dr. Asimov’s other books, readers will find this adventure in time-telling stimulating and absorbing.

This is among my favorites of the Abelard-Schuman science juveniles and a book which remains refreshingly current thirty-five years after it was written. It also represents a bit of a departure for Asimov, because it is one of his first science books not about chemistry or its close friend, physics.

It’s about time—timepieces, measuring time, calendars, weeks, months, years. It’s a subject which has an important impact on our daily lives, one full of odd and arcane little rules that nobody can remember, and one which is fascinating and fun to disentangle.

This is definitely a book which anybody interested in history or chronology should read.

Of course, it is not flawless, even aside from the blatant lie the publishers made Asimov tell. (He once called a friend on the West Coast, taking care to call early in the morning Boston time so that it would be mid-morning where the friend lived. Unfortunately, he added three hours instead of subtracting them and ended up calling his friend in the wee hours of the morning. This incident was what ultimately brought the book about. The publisher liked the story but insisted that it be reversed, so that it was the friend who made the call, the friend who made the mistake, and the friend who ended up waking someone from a deep slumber. They thought the truth would reflect badly on the author of a book about how time is kept.)

The main problem, of course, is forced on it by its genre—it’s a juvenile, intended for an early-teenage audience, so there’s a lot of fascinating stuff that Asimov left out.

A secondary problem to which I am particularly sensitive because of my academic background is its eurocentricity. This is only to be expected, of course, from a book by an American author for an American audience in the 1950’s, and I certainly don’t think Asimov did it out of a hidden feeling that Asians are inferior to Europeans. Indeed, the only reason why I deplore it is because there is so much fascinating information about how time was reckoned in parts of the world Asimov doesn’t discuss which is every bit as fun as what he does say.