- TWILIGHT, the transition period between day and night, called in the Bible bein ha-arbayim (Heb. בֵּין הָעַרְבַּיִם, Ex. 12:6), and in rabbinic literature bein ha-shemashot (Heb. בֵּין הַשְּׁמָשׁוֹת, Ber. 2b; Avot 5:9). Whether twilight forms part of day or the night is a moot question in the Talmud (Shab. 34b). Its exact duration was also a matter of dispute. According to R. yose , the transition from day to night is instantaneous, whereas R. Nehemiah said twilight lasted for nine minutes after sunset (i.e., the length of a walk of half a mile = 1000 ells, approx. 560 meters). The amora Samuel said it lasts for 13½ minutes and according to another opinion 12 minutes (Shab. 34b). The codifiers established the duration of twilight at 18 minutes, i.e., when the sun is about 3½ degrees below the horizon (Tur, OḤ 293). Actual night begins only with the appearance of three stars in the sky (called ẓet ha-kokhavim, Ber. 2b; see also Neh. 4:15). This traditional calculation of the duration of twilight deviates only slightly from the exact astronomical twilight. Twilight on Friday is reckoned as Sabbath eve and consequently no work may be performed then. The Sabbath candles must be lit before twilight (Shab. 2:7). The twilight at the end of the Sabbath is calculated as still belonging to the Sabbath day which concludes with the appearance of three stars in the sky. This rule applies also to the beginning and conclusion of the holidays. Before the beginning of the Day of Atonement, twilight is reckoned from approximately one hour before the stars would become visible. All religious ceremonies which ought to be performed only at night, e.g., the recital of the evening service, the kindling of Ḥanukkah lights , the reading of the megillah , should be observed only after twilight; but if they are performed during twilight they are valid and do not have to be repeated. -BIBLIOGRAPHY: Sh. Ar., OḤ 261:1–3; Eisenstein, Dinim, 39; JE, 3 (1903), 501; 11 (1905), 591–7; ET, 3 (1951), 121–9, S.V. Bein ha-Shemashot.
Encyclopedia Judaica. 1971.