Once upon a time, it didn’t matter if a clock tower in Spoleto kept time slightly differently than a tower in Assisi and far differently than one in Rome. In Why Time Flies we read about the experts in Greenwich who run data from 80 labs around the world into an algorithm that favors the more accurate clocks. The process of arriving at “Coordinated Universal Time” takes five days: “The world clock exists only on paper and only in retrospect; .  .  . it is a newsletter called Circular T,” Alan Burdick tells us. The newsletter comes monthly, and people running clocks around the world tweak them to get closer in the next month. There is no perfect timekeeper.

Burdick takes his time elegantly explaining its mysteries as a human phenomenon, blending philosophy, history, psychology, and candid introspection. The time he cares about is a “property of the mind,” a bodily function and a social agreement.