MARKING TIME

A topical but pedantic study of how our calendar’s development has owed as much to human choice as scientific precision. Australian astronomer Steel (Rogue Asteroids and Doomsday Comets, 1995) explains the origins of the Western calendar. It’s a story of incremental change, with contributions from such famous figures as Julius Caesar, The Venerable Bede, Pope Gregory XIII, and Isaac Newton. Steel contends that our “imperfect” calendar is a product of “the intricacies of astronomy, history, and human foibles.” Other civilizations have chosen different calendars. The ancient Egyptians, for example, based their calendar on the flooding of the Nile. Islamic nations use the moon. By necessity, Steel’s narrative is as much about history as science. We learn that Julius Caesar decreed the 365-day year and divided it into months. Alas, the Julian calendar created problems because it was slightly too long. In 1582, Pope Gregory XIII decreed the Gregorian calendar, which deleted ten days from the old system. Some Protestant nations, like England, rejected the Gregorian calendar until the 18th century. While astronomers will find Steel’s narrative lucid, the non-scientist can expect some heavy lifting. For example, Steel tells us that the ancient Greek astronomer Callippus “suggested that the year should be precisely 365.25 days long on average, and invented a cycle of 4 X 19 = 76 years from which one day was deleted, the 76 years thus lasting for (4 X 6,940) - 1 = 27,759 days spread over 940 months.” This sort of sentence is sure to try the non-mathematicians’ patience. That said, Steel provides some fascinating history, such as how daylight savings time originated as a wartime necessity and how Greenwich Mean Time became the universal standard. With the year 2000 on the horizon, Steel hits the shelves at an opportune time; unfortunately, the general reader will have to look elsewhere for a more accessible history of our often illogical calendar.