WEEK (Hebr. "shabua'," plural "shabu'im," "shabu'ot"; Aramaic, "shabbeta," "shabba"; N. T. Greek, σάββατον, σάββαατα):
A division of time comprising seven days, thus explaining the Hebrew name. There are indications of the use of another system of reckoning time, in which the month was divided into three parts of ten days each, the decade being designated in Hebrew by the term " 'asor" (Gen. xxiv. 55; comp. the commentaries of Dillmann and Holzinger ad loc.; Ex. xii. 3; Lev. xvi. 29, xxiii. 27, xxv. 9). This apparently represented one-third of the solar month, while the week of seven days was connected with the lunar month, of which it is, approximately, a fourth. The quadripartite division of the month was evidently in use among the Hebrews and other ancient peoples; but it is not clear whether it originated among the former. It is unnecessary to assume, however, that it was derived from the Babylonians, for it is equally possible that observations of the four phases of the moon led the Hebrew nomads spontaneously and independently to devise the system of dividing the interval between the successive new moons into four groups of seven days each. There is ground, on the other hand, for the assumption that both among the Babylonians and among the Hebrews the first day of the first week of the month was always reckoned as coincident with the first day of the month. The emphasis laid on the requirement (Lev. xxiii. 15) that the weeks of Pentecost should be "complete" ("temimot") suggests that weeks might be reckoned in such a way as to violate this injunction. This was the case as long as the first day of the first week of the month was made to coincide with the new moon. At the end of four weeks an interval of one or two days might intervene before the new week could begin. At an early date, however, this intimate connection between the week and the moon must have been dissolved, the chief cause of the fixed week of seven days being, in all probability, the predominance of the seventh day as the Sabbath (but see Meinhold, "Sabbat und Woche im O. T." Göttingen, 1905, according to whom Sabbath, originally only the full-moon day and the week areindependent of each other). The week thus became a useful standard in the measurement of intervals of time (one week, Gen. xxix. 27 et seq.; two weeks, Lev. xii. 5; three weeks, Dan. x. 2; seven weeks, Deut. xvi. 9; Lev. xxiii. 15).Week-Days Not Named.
With the exception of the seventh day, which was called the Sabbath, the days of the week were designated by ordinal numerals, not by names. In post-Biblical and later Hebrew literature Friday is known as " 'Ereb Shabbat" (Greek, παρασκευή or προσāββατον; Judith viii. 6; Mark xv. 42; Matt. xxvii. 62; Josephus, "Ant." xvi. 6, § 2). The Biblical writings contain no trace of any custom of naming the days of the week after the seven planets; nor had this custom, found among the Babylonians and the Sabeans, any bearing originally on the division of the week into seven days, since it was a mere numerical coincidence that seven planets were assumed in these primitive astrological conceits. In the Babylonian nomenclature the first day of the week was under the tutelage of Shamash, the sun; the second under that of Sin, the moon; the third under Nergal, Mars; the fourth under Nabu, Mercury; the fifth under Marduk (Bel), Jupiter; the sixth under Ishtar (Beltis), Venus; and the seventh under Ninib, Saturn (see, however, Schrader, "K. A. T." 3d ed., pp. 622 et seq.).