1911 Encyclopædia Britannica/Week
WEEK (from A.S. wicu, Germanic *wikôn, probably = change, turn), the name given to periods of time, varying in length in different parts of the world, but shorter than a “month.” The month may be divided in two ways: a fractional part may be taken (decad or pentad), as in East Africa or Ancient Egypt (moon-week), or the week may be settled without regard to the length of the month (market-week, &c.). The seven-day week (see Calendar) originated in West Asia, spread to Europe and later to North Africa (Mahommedan). In other parts of Africa three, four (especially in the Congo), five, six and eight (double four) day weeks are found, and always in association with the market; the same applies to the three-day week of the Muyscas (S. America), the four-day week of the Chibchas, the five-day week of Persia, Malaysia, Java, Celebes, New Guinea and Mexico; in ancient Scandinavia a five-day period was in use, but markets were probably unknown. That the recurrence of the market determined the length of the week seems clear from the Wajagga custom of naming the days after the markets they visit, as well as from the fact that on the Congo the word for week is the same as the word for market. Among agricultural tribes in Africa one day of the week, which varies from place to place, is often a rest-day, visiting the market being the only work allowed.
(N. W. T.)