Ancient Egyptians divided daylight into twelve parts, which helped shape the twelve-hour clock.

The longer version

Egyptian timekeepers split the sunlit span into twelve, tracking them with shadow clocks and later with devices that let water drip from dawn. Because daylength changes with season, those hours stretched in summer and shrank in winter. Priests needed the divisions to schedule rituals after dark.

Twelve likely came from finger-counting: three knuckles on each of four fingers give twelve units, a scheme used across the ancient Mediterranean. Night was also divided, often into twelve watches. Fixed equal hours arrived later with mechanical clocks, which had to reconcile a steady mechanism with an old variable scheme. The twelve-hour dial persisted even though its original meaning was gone.

Where this entry sits

These facts wander through clocks, calendars, time zones, and the long human effort to measure passing hours. You will find leap years, odd month lengths, ancient sundials, and the reasons modern timekeeping works the way it does. The full list sits on the Time and Calendars page, where every entry is listed in order.