The canonical hours, which had measured out the daylight into the appropriate elastic units between divine services, were registered on clocks until about the fourteenth century. It was around 1330 that the hour became our modern hour, one of twenty-four equal parts of a day. This new “day” included the night. It was measured by the time between one noon and the next, or, more precisely, what modern astronomers call “mean solar time.” For the first time in history, an “hour” took on a precise, year-round, everywhere meaning.
