wice

Old English wice (also wucu, wicu) comes from Proto-Germanic *wikō, whose deeper origins are disputed. One theory traces it to PIE *weik-, meaning to bend or turn — a week being a turning point, a unit after which time bends back and starts again. Another connects it to a root meaning change or alternation. Either way, the concept is cyclical: the week is a wheel, and every seven days it completes a rotation.

But why seven? The Babylonians. By around 700 BCE, Babylonian astronomers had identified seven celestial bodies visible to the naked eye: the Sun, the Moon, Mars, Mercury, Jupiter, Venus, and Saturn. Each was assigned to a day. The Romans adopted this system, naming the days after their equivalents: dies Solis, dies Lunae, dies Martis, and so on. Germanic peoples translated some of these into their own gods — Tiw for Mars (Tuesday), Woden for Mercury (Wednesday), Thor for Jupiter (Thursday), Frigg for Venus (Friday). Saturday, Sunday, and Monday kept their Roman-celestial names.

The seven-day week has no astronomical basis. A month roughly tracks the moon. A year tracks the sun. A day tracks the Earth's rotation. But a week tracks nothing. It is pure convention — a Babylonian convention, adopted by Jews, inherited by Christians and Muslims, and now used worldwide. Emperor Constantine made the seven-day week official in the Roman Empire in 321 CE, and it has not been seriously challenged since.

The French Revolutionary calendar tried to replace the week with a ten-day décade in 1793. It lasted twelve years. The Soviet Union tried a five-day week in 1929, then a six-day week in 1931. Both failed. The seven-day week survived the French Revolution, the Russian Revolution, and every attempt at rational reform. Babylonian astronomers set the rhythm of modern life, and three thousand years later, nobody can change it.