"Day," yom; ordinarily, the Hebrew "day" lasted from dawn to the coming forth of the starts (Ne 4:21). The context usually makes it clear whether the term "day" refers to the period of twenty-four hours or to daytime; when there was a possibility of confusion, the term laylah, "night," was added (Ge 7:4,12; 31:39). The "day" is reckoned from evening to evening, in accordance with the order noted in the account of Creation, namely, "And there was evening and there was morning, one day" (Ge 1:5); Le 23:32 and Da 8:14 reflect the same mode of reckoning the day. The phrase ?erebh boker, "evening-morning," used in this last passage, is simply a variation of yom and laylah, "day" and "night"; it is the equivalent of the Greek nuchthemeron (2Co 11:25). That the custom of reckoning the day as beginning in the evening and lasting until the following evening was probably of late origin is shown by the phrase "tarry all night" (Jud 19:6-9); the context shows that the day is regarded as beginning in the morning; in the evening the day "declined," and until the new day (morning) arrived it was necessary to "tarry all night" (compare also Nu 11:32).

The transition of day to night begins before sunset and lasts till after sunset; the change of night to day begins before sunrise and continues until after sunrise. In both cases, neither ?erebh, "evening," nor boqer, "morning," indicate an exact space of time (compare Ge 8:11; Ex 10:13; De 16:6).

The term nesheph, is used for both evening twilight and morning dawn (compare 1Sa 30:17; 2Ki 7:5,7; Job 7:4). Since there were no definite measurements of the time of day, the various periods were indicated by the natural changes of the day; thus "midday" was the time of the day when the sun mounted its highest (cohorayim); afternoon was that part of the day when the sun declined ( neToth ha-yom); and evening was the time of the going down of the sun (?erebh). "Between the evenings" (ben ha-?arbayim) was the interval between sunset and darkness. The day was not divided into hours until a late period. [~sha?ah = Aramaic] (Da 3:6), is common in Syriac and in later Hebrew; it denoted, originally, any short space of time, and only later came to be equivalent to our "hour" (Driver). The threefold division of the day into watches continued into post-exilic Roman times; but the Roman method of four divisions was also known (Mr 13:35), where all four divisions are referred to: "at even" (opse), "midnight" (mesonuktion), "at cock crowing" (alektorophonia), "in the morning" (proi). These last extended from six to six o'clock (of also Mt 14:25; Mr 13:35). Ac 12:4 speaks of four parties of four Roman soldiers (quaternions), each of whom had to keep guard during one watch of the night. In Berakhoth 3b, Rabbi Nathan (2nd century) knows of only three night-watches; but the patriarch, Rabbi Judah, knows four.