Hindu civilization employed a seven-day week, mentioned in the Ramayana, a sacred epic written in Sanskrit about 500 BC, as Bhanu-vaar meaning Sunday, Soma-vaar meaning Moon-day and so forth.
The ancient Babylonians observed a seven-day week, stemming from astronomical observation and association. Days and deities were based on the seven heavenly bodies or ”luminaries” visible to the naked eye (the Sun, Moon, and 5 visible planets).
Other theories speculate that the fixed seven-day period appeared due to evenly dividing a lunar month into quarters.
The Hebrew (and later Christian) seven-day week corresponds to the biblical creation story, in which God created the universe in six days, then rested on the seventh.