Weeks of seven days were used in ancient Babylon and later adopted widely elsewhere.

The longer version

Seven came from counting the moving lights in the sky that seemed to wander: sun, moon and five planets visible to the naked eye. Babylonian practice gave each day a character tied to those bodies, and astrologers used the sequence to plan rituals and predict omens.

Unlike months tied to the moon or years tied to the sun, this cycle has no astronomical anchor, so it simply repeats without drifting. That independence made it easy to carry into other systems, and Jewish, Christian and later Islamic practice all kept it, spreading it far beyond its origin.

Where this entry sits

This set looks at ancient civilizations, old inventions, trade routes, calendars, and the ordinary objects people once used every day. Nothing here is advice or opinion, just short notes about how daily life used to be organised long ago. The full list sits on the History page, where every entry is listed in order.