Why Does a Week Have 7 Days?

week, period of seven days, a unit of time artificially devised with no astronomical basis. The week's origin is generally associated with the ancient Jews and the biblical account of the Creation, according to which God laboured for six days and rested on the seventh.

Why do we have 7 days in a week?

The Babylonians, who lived in modern-day Iraq, were astute observers and interpreters of the heavens, and it is largely thanks to them that our weeks are seven days long. The reason they adopted the number seven was that they observed seven celestial bodies — the Sun, the Moon, Mercury, Venus, Mars, Jupiter and Saturn.

When did the 7 day week originate?

The seven-day week originates from the calendar of the Babylonians, which in turn is based on a Sumerian calendar dated to 21st-century B.C. Seven days corresponds to the time it takes for a moon to transition between each phase: full, waning half, new and waxing half.