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Relative hour (Hebrew singular: shaʿah zǝmanit / שעה זמנית; plural: shaʿot - zǝmaniyot / שעות זמניות), sometimes called halachic hour, temporal hour, seasonal hour and variable hour, is a term used in rabbinic Jewish law that assigns 12 hours to each day and 12 hours to each night, all throughout the year. A relative hour has no fixed length in absolute time, but changes with the length of daylight each day - depending on summer (when the days are long and the nights are short), and in winter (when the days are short and the nights are long). Even so, in all seasons a day is always divided into 12 hours, and a night is always divided into 12 hours, which invariably makes for a longer hour or a shorter hour. At Mediterranean latitude, one hour can be about 45 minutes at the winter solstice, and 75 minutes at summer solstice. All of the hours mentioned by the Sages in either the Mishnah or Talmud, or in other rabbinic writings, refer strictly to relative hours.

Another feature of this ancient practice is that, unlike the standard modern 12-hour clock that assigns 12 o'clock pm for noon time, in the ancient Jewish tradition noon time was always the sixth hour of the day, whereas the first hour began with the break of dawn according to many Halachic authorities, and with sunrise according to others. Midnight (12:00 am local official clock time) was also the sixth hour of the night, which, depending on summer or winter, can come before or after 12:00 am local official clock time, whereas the first hour of the night always begins after sunset, when the first three stars appeared in the night sky.

During the Spring (באחד בתקופת ניסן‎) and Autumnal (באחד בתקופת תשרי‎) equinox (around 20 March and 23 September), the length of a day and night are equal. However, even during the summer solstice and winter solstice when the length of the day and the length of the night are at their greatest disparity, both day and night are always divided into 12 hours.

History

Temporal hours were common in many cultures. A division of day and night into twelve hours each was first recorded in Ancient Egypt. A similar division of day and night was later made in the Mediterranean basin from about Classical Greek Antiquity into twelve temporal hours each (Ancient Greek: ὥραι καιρικαί, romanized: horai kairikai).

In Western culture they were adopted from the Roman calendar and were adopted in the European Medieval era. They had particular relevance in the fixed daily schedule of the monastic orders. This division of time allowed the work of the day -such as eating, praying, or working -to always be performed at the same (temporal) hour, regardless of season (Prayer of the Hours).

Jewish tradition

The prevailing opinion is that each day begins at the rise of dawn (Heb. עלות השחר‎), which is about 72 minutes before sunrise, yet, for practical reasons in some biblically related commandments, some scholars begin counting the hours of the day from sunrise (Heb. הנץ החמה‎), such as for the recital of Shema' which, as a first resort, must be recited when a person rises from his sleep in the morning, a time that is traditionally linked with sunrise, and continuing thereafter until the beginning of the 4th hour of the day, or, for example, when burning leaven on the 14th day of the lunar month Nisan, which must be burnt in the 6th hour of the day when counting from sunrise. At this time, the sun is nearly at its apex.

The commencement of nightfall is not as divisive in Jewish law:

Rabbi Pinchas said in the name of Rabbi Abba bar Pappa: One star is certainly day; two is a doubtful case; three is certainly night.

The precise, intermediate time between day and night, or what is termed in Hebrew bayn ha-sh'meshot, has been discussed by Talmudic scholars in great detail. Some describe the time as when the evening sky turns a silverish-grey color. The same time is described by Moses Alashkar as "from the moment that the entire circle of the sun sets until there appear three medium-sized stars." The duration of this time is generally held to be about 12 minutes, but which, with respect to the Sabbath day, is given a more stringent application, namely, 13.5 minutes after sunset. Rabbeinu Tam, disputing, held the time of bayn ha-sh'meshot to be 58.5 minutes. A third opinion is that of Maimonides who puts the time of bayn ha-sh'meshot at the time it takes to walk 3⁄4 of a biblical mile, a time which Maimonides estimates at about 18 minutes (temporal hours), according to what they have understood from the words of Maimonides, namely, that a person traverses a biblical mile in 24 minutes. This was the custom of the cities of Yemen.

Disputations

In old times, the hour was detected by observation of the position of the sun, or when the first three stars appeared in the night sky. During the first six hours of the day, the sun is seen in the eastern sky. At the sixth hour, the sun is always at its zenith in the sky, meaning, it is either directly overhead, or parallel (depending on the hemisphere). Those persons living in the Northern Hemisphere, the sun at noon time will appear overhead slightly towards the south, whereas for those living in the Southern Hemisphere, the sun at noon time will appear overhead slightly towards the north (an exception being in the tropics, the sun can sometimes be directly overhead). From the 6th and a half hour to the 12th hour, the sun inclines towards the west, until it sets. The conclusion of a day at the end of twilight may slightly vary in minutes from place to place, depending on the elevation and the terrain. Typically, nightfall ushers in more quickly in the low-lying valleys, than it does on a high mountaintop.

There are two major opinions how to calculate these times:

• The Magen Avraham (Shulhan Arukh, Orach Chaim 58:1) holds that because one may do "daytime" activities between daybreak and nightfall, one calculates the day from daybreak (מעלות השחר‎) to nightfall, and divides that period into twelve parts. Although this is known as the opinion of the Magen Avraham, he only says it explicitly with regards to the Recital of the Shema because the time for that mitzvah begins at ʿalot hashachar ("break of dawn"). Nevertheless, this is the opinion of Tosafot, the Rashba, the Ritva, the Ra'ah, the Terumat ha-deshen, the Bach, the Eliyah Rabba, and the Pri Chadash regarding all of the times of the day. Usually this time is computed using daybreak as 72 minutes before sunrise - or more accurately using when the sun is 16.1 degrees below the horizon, as it is in Jerusalem at the equinox 72 minutes before sunrise - before sunrise, and nightfall as 72 minutes after sunset. However, the common practice in Jerusalem (following the Tucazinsky luach) is to compute it using 20 degrees (90 minutes at the equinox).
• Another variation of this opinion is to consider the day as beginning at daybreak (מעלות השחר‎), reckoning the "first hour" of the day with the rise of dawn (Hebrew: עמוד השחר), that is to say, approximately 72 minutes before sunrise, and the end of the day commencing shortly after sunset when the first three medium-size stars have appeared in the night sky. From the moment of sunset when the sun is no longer visible until the appearance of the first three medium-size stars is a unit of time called evening twilight (Hebrew: בין השמשות). In the Talmud, twilight is estimated at being the time that it takes a person to walk three quarters of a biblical mile (i.e. 1,500 cubits, insofar that a biblical mile is equal to 2,000 cubits). According to Maran's Shulhan Arukh, a man traverses a biblical mile in 18 minutes, meaning, one is able to walk three quarters of a mile in 13½ minutes. According to Maimonides, a man walks a biblical mile in 24 minutes, meaning, three quarters of a mile is done in 18 minutes. In Jewish law, the short period of dusk or twilight (from the moment the sun has disappeared over the horizon until the appearance of the first three stars) is a space of time whose designation is doubtful, partly considered day and partly considered night. When the first medium-size star appears in the night sky, it is still considered day; when the second star appears, it is an ambiguous case. When the third star appears, it is the beginning of the first hour of the night. Between the break of dawn and the first three medium-size stars that appear in the night sky there are always 12 hours. This version of this opinion is followed by many Sephardic communities. Nevertheless, Rabbi Yehosef Schwartz, Rabbi Yechiel Michel Tucazinsky, Rabbi Avraham Chaim Naeh, Rabbi Yitzchok Yaakov Weiss, Rabbi Aharon Kotler and many others reject this opinion because it causes "midday" to be at a time when the sun is not at its highest point, and the Talmud says explicitly that the sun is at its highest point at noon (Heb. chatzot). These poskim thus insist that even if one would rule according to the Geonim with regards to the emergence of stars, the time of the day are computed using tzeit kol ha-kokhavim in order to make midday when the sun is at its highest point.
• The Vilna Gaon holds that although "daytime" activities can start as early as daybreak and end as late as nightfall, their proper time lechatchila (ab initio) is from sunrise to sunset, so one calculates the day from sunrise to sunset and divides that period into twelve parts. This is also the opinion of Rav Nisim Gaon, Rav Saadya Gaon, Rav Hai Gaon, Rabbeinu Chananel, Maimonides, Rabbeinu Yonah, and the Levush. In Roman times, these daylight hours were known as unequal hours.

In the Modern Age of astral science and of precise astronomical calculations, it is now possible to determine the length of the ever-changing hour by simple mathematics. To determine the length of each relative hour, one needs but simply know two variables: (a) the precise time of sunrise, and (b) the precise time of sunset. Since according to the first opinion, the day begins approximately 72 minutes before sunrise and ends approximately 72 minutes after sunset (and according to the variant understanding of this opinion, ends approximately 13½ or 18 minutes after sunset), or begins at sunrise and ends at sunrise according to the second opinion, by collecting the total number of minutes in any given day and dividing the total number of minutes by 12, the quotient that one is left with is the number of minutes to each hour. In summer months, when the days are long, the length of each hour during daytime can be quite long depending on one's latitude, whereas the length of each hour during nighttime can be quite short again depending on one's latitude. It should also be noted that according to those opinions that the 72 minutes are computed according to 16.1 degrees, the further one goes from the equator, the longer it will get, such that in northern latitudes it could become 2 hours or longer.

Practical bearing

In Jewish Halacha, the practical bearing of this teaching is reflected in many halachic practices. For example, according to Jewish law, the morning recitation of Kriyat Shema must be made between slightly before sunrise and the end of the third hour of the day, a time that actually fluctuates on the standard 12-hour clock, depending on the time of year. Its application is also used in determining the time of the Morning Prayer, which must be recited between sunrise until the end of the fourth hour, but post facto can be said until noon time, and which times will vary if one were to rely solely on the dials of the standard 12-hour clock, depending on the seasons.

On the eve of Passover, chametz can only be eaten until the end of the fourth-hour of the day, and must be disposed of by the end of the fifth hour.

In Jewish tradition, prayers were usually offered at the time of the daily whole-burnt offerings. The historian, Josephus, writing about the daily whole-burnt offering, says that it was offered twice each day, in the morning and about the ninth hour. The Mishnah, a compendium of Jewish oral laws compiled in the late 2nd-century CE, says of the morning daily offering that it was offered in the fourth hour, but says of the late afternoon offering: "The daily whole-burnt offering was slaughtered at a half after the eighth hour, and offered up at a half after the ninth hour." Elsewhere, when describing the slaughter of the Passover offerings on the eve of Passover (the 14th day of the lunar month Nisan), Josephus writes: "...their feast which is called the Passover, when they slay their sacrifices, from the ninth hour to the eleventh, etc." (roughly corresponding to 3 o'clock pm to 5 o'clock pm). Conversely, the Mishnah states that on the eve of Passover the daily whole-burnt offering was slaughtered at a half past the seventh hour, and offered up at a half past the eighth hour.

See also

• Zmanim
• Lunar calendar
• Hebrew calendar
• Biblical and Talmudic units of measurement
• Roman timekeeping
• Traditional Chinese timekeeping
• Japanese clock

Further reading

• Sar-Shalom, Rahamim (1984). She'harim La'Luah Ha'ivry (Gates to the Hebrew Calendar) (in Hebrew). Tel-Aviv. p. 96 (Relative hours). OCLC 854906532.{{cite book}}: CS1 maint: location missing publisher (link)

References

1. Maimonides (1989). Jehoshua Blau (ed.). R. Moses b. Maimon Responsa (in Hebrew). Vol. 1 (2 ed.). Jerusalem: Meḳize Nirdamim / Rubin Mass. pp. 251–255 (responsum no. 134). OCLC 78411726.
2. Maimonides (1963). Mishnah, with Maimonides' Commentary (in Hebrew). Vol. 1. Translated by Yosef Qafih. Jerusalem: Mossad Harav Kook. p. 33 (Berakhot 1:5). OCLC 233308346.
3. Yaakov de Castro, `Erekh Leḥem (Orach Chaim §233:2)
4. Laurence, Ray (2006). Roman Pompeii: Space and Society. Routledge. pp. 104–112. ISBN 978-1-134-76899-8. Retrieved 24 December 2019.
5. Maimonides (1963). Mishnah, with Maimonides' Commentary (in Hebrew). Vol. 1. Translated by Yosef Qafih. Jerusalem: Mossad Harav Kook. p. 33 (Berakhot 1:5). OCLC 233308346. Be apprised that all of the hours that are mentioned throughout all the Mishnah are none other than relative hours, and the word relative has the connotation of those hours wherein there are twelve in the daytime, as also at night.
6. Magen Avraham §58:1, §233:3 of R. Avraham Gombiner; Maimonides' commentary on Mishnah Megillah 2:4; the Responsa Terumat HaDeshen, responsum # 1 of R. Israel Isserlein; the Levush §267 of R. Mordecai Yoffe; Minchat Kohen (Mevoh Shemesh 2:6) of R. Abraham Cohen Pimentel, in the name of Tosefot Ha-Ramban (Nachmanides) and R. Shlomo ben Aderet (Rashba); Bayit Chadash §431 of R. Joel Sirkis; Turei Zahav §433 of R. David HaLevi Segal; Pri Chadash §433 of R. Hezekiah da Silva; Eliyahu Rabbah 58:2 of R. Elijah Spira; Mizbe’ach Adamah 4a of R. Mordechai Chaim Meyuchas; Mikra'ei Kodesh 158b by R. Baruch Gigi; Mateh Yehuda §433 of R. Yehudah Ayash; the Responsa Hayim Sha'al 2:38 (70) of R. Chaim Yosef David Azulai; Tov Ayin 18:38 of R. Alter Yechiel Naiman; Chayei Adam 21:3, 27:1 of R. Avraham Danzig; Kitzur Shulhan Arukh 17:1 of R. Shlomo Ganzfried, Chesed La'alafim 58:5 of R. Eliezer Papo; Shiltei ha-Gibborim 58:3 of Joshua Boaz ben Simon Baruch; Rav Poalim (Orach Chaim 2:2); Shalmei Tzibbur 93c of R. Yisrael Ya'akov Algazi, among others. Rabbi Yechiel Michel Tukachinsky in Sefer Eretz Yisrael (p. 18:3) has written that the custom of the Land of Israel is to follow the Magen Avraham and only under extenuating circumstances may one rely on the Vilna Gaon.
7. The Vilna Gaon, as cited in Bi'urei ha-Gra ("Elucidations of the Gra") §459:2, but also the opinion of Rabbi Hai Gaon and many other authorities cited in the next section.
8. Jerusalem Talmud (Berakhot 1:1)
9. ^ Karlheinz Deußer: Temporaluhren: Die Suche nach mechanischen Uhren, die mit Temporalstunden liefen. In: Jahresschrift der deutschen Gesellschaft für Chronometrie. Band 51, 2012, S. 143–160; Jürgen Osing: Hieratische Papyri aus Tebtunis I (Carsten Niebuhr Institute of Ancient Eastern Studies Copenhagen). Museum Tusculanum Press, Copenhagen 1998, ISBN 8-7728-9280-3; Rudolf Wendorff: Zeit und Kultur. Geschichte des Zeitbewusstseins in Europa. Westdeutscher Vlg, Wiesbaden 1980,ISBN 3-531-11515-4
10. Babylonian Talmud, Berakhot 59b, Rashi s.v. שבתאי; Mishnah Berakhot 1:1
11. Babylonian Talmud, Megillah 20a, Rashi, s.v. עד הנץ החמה
12. Abraham of Narbonne (1867). Sefer ha-Eškol (in Hebrew). Vol. 1. Halberstadt: H. Meyer. p. 10 (Hil. Tefillah ve-Ḳiryat Shema). OCLC 774954727. At sunrise, the principal part of the day begins, and it is one's duty to pray when the sun comes out, as it says: 'They shall fear you while the sun endures' (Psalm 72:5). Even though the break of dawn (ʻamūd ha-shaḥar) is considered day for all things, just as we say in chapter 2 of Megillah , as a first resort, the principal part of day is reckoned from the moment the rays of the sun appear and the majority of people have risen at that hour, for we call 'and when you rise up' (Deut. 6:7)
13. Maimonides (1963). Mishnah, with Maimonides' Commentary (in Hebrew). Vol. 1. Translated by Yosef Qafih. Jerusalem: Mossad Harav Kook. p. 232 (Megillah 2:4). OCLC 233308346. We have reckoned the day from the rise of dawn, since it says in Ezra 'from the break of dawn until the stars came out' (Nehemiah 4:15 ). Now he called this 'day', when he said of it, 'in the night they were unto us a guard, while the day labour'
14. Magen Avraham on Shulchan Aruch (Orach Chayim §58:1)
15. Maimonides (1963). Mishnah, with Maimonides' Commentary (in Hebrew). Vol. 1. Translated by Yosef Qafih. Jerusalem: Mossad Harav Kook. p. 32 (Berakhot 1:1). OCLC 233308346.
16. Mordecai Yoffe, Levush Malkhus (Orach Chayim, sections 233:1, 266)
17. Tukatzinsky, Yechiel Michel (1928). Sefer Bein ha-Shemashos (in Hebrew). Jerusalem. pp. 97-98. OCLC 233065543. The opinion of our Rabbi, the Vilna Gaon, as well as of many other poskim, is that in all the halachic matters touching on the hours , we reckon from sunrise until sunset, such as the latest time Kiryat Shema, a quarter of the day (a third of the hours), and the latest time of the prayer, a third of the day (four hours), and the latest time eating leaven on the eve of Passover, a third of the day, and the burning of leaven in another relative hour – all from sunrise until sunset. ...The practice is to be stringent in accordance with the Vilna Gaon's method when it comes to the latest time Kiryat Shema, and the prayer, and when it comes to eating and burning the leaven .{{cite book}}: CS1 maint: location missing publisher (link)
18. Chaim Yosef David Azulai, in Ḥayim Sha'al, is one exception to this rule, who wrote in Part II, section 38, item 70 that the hours three and four prescribed for the recital of the Shema and for the prayer begin from the break of dawn, rather than from sunrise. This view was also held by Rabbi Yosef Qafih.
19. Rabbeinu Chananel (1990). David Metsger (ed.). Rabbeinu Ḥananel bar Ḥushiʼel's Commentary on the Talmud (Berakhot) (in Hebrew). Jerusalem: Mekhon "Lev Sameach". p. 53 (Berakhot 26a). OCLC 741094222.
20. Maimonides, Mishneh Torah (Hil. Kiryat Shema 1:10–13)
21. Shulchan Aruch (Orach Chayim 58:1)
22. Babylonian Talmud, Pesahim 12b; Ahai of Shabha (1971). Sheiltot of Rab Aḥai Gaon. Jerusalem: Makor Ltd. p. 31a (Pesach), column 122, section 74. OCLC 762430858., a facsimile, printed from the first Venice edition (MS. 1546)
23. Jerusalem Talmud (Berakhot 1:1 )
24. de Castro, Yaakov (1718). ʻErekh Leḥem (in Hebrew). Istanbul: Kushṭa. p. 9a (Orach Chayim, section 260:2). OCLC 762370388. (reprinted in 1988)
25. Al-ʻAdani, Saʻid ben Daṿid (2009). Zephaniah Sharʻabi (ed.). Perush Rabenu Saʻid n. Daṿid al-ʻAdani ʻal Mishneh Torah leha-Rambam (Sefer Ahavah) (in Hebrew). Translated by Pinḥas ben Yosef Ḳoraḥ. Ḳiryat Sefer: Mekhon Marʻeh. p. 253. OCLC 429339490. It is known that bayn ha-sh'meshot is a case of doubt whether it is day or night, and they treat it with stringency in every place, the estimation of which time being approximately one-third of an hour after sunset (18 minutes), being from the moment the sun has completely gone down until the appearance of three stars, just as it has been explained in chapter 5 of Hilkot Shabbat (sect. 4).
26. Babylonian Talmud (Shabbat 34b–35a); cf. Moses Alashkar, Responsa (responsum # 96), Sabbionetta, 1553; Gelis, Jacob (1968). The Customs of the Land of Israel (מנהגי ארץ-ישראל) (in Hebrew). Jerusalem: Mossad Harav Kook. pp. 99-100 (§ 12). OCLC 873519965.; Yaakov de Castro, Erekh Lehem (Orach Chayim, section 260:2); Isaac of Corbeil (Sefer Mitzvot Ḳatan); Ibn Abi-Zimra, David (1882). Aharon Wolden (ed.). The Responsa of the Radbaz (in Hebrew). Vol. 2. Warsaw. OCLC 233235313.{{cite book}}: CS1 maint: location missing publisher (link), s.v. part IV, responsum # 1353 (reprinted in Israel, n.d.)
27. Yosef, Ovadia (2002). Halikhot ʻOlam (in Hebrew). Vol. 3. Jerusalem: Mekhon "Meʼor Yiśraʼel". p. 140. OCLC 39937409.
28. Yosef, Ovadia (2002). Halikhot ʻOlam (in Hebrew). Vol. 5. Jerusalem: Mekhon "Meʼor Yiśraʼel". p. 59. OCLC 39937409.
29. Gelis, Jacob (1968). The Customs of the Land of Israel (מנהגי ארץ-ישראל) (in Hebrew). Jerusalem: Mossad Harav Kook. p. 98 (§ 12). OCLC 873519965.
30. Yosef, Ovadia (2003). Ḥazon ʻOvadyah (in Hebrew). Vol. 1. Jerusalem: Mekhon "Meʼor Yiśraʼel". pp. 264–ff.
31. Rabbeinu Tam (1811). Sefer Ha-yashar (in Hebrew). Vienna. pp. 19b (section 181).
32. ^ Al-ʻAdeni, Saʻīd ben David (2009). Pinhas Qorah (ed.). Commentary of Rabbeinu Saʻīd ben David al-ʻAdeni (On the Mishneh Torah of Maimonides, Sefer Ahavah) (in Hebrew). Kiryat Sefer: Mekhon Mar'eh. p. 243 (note 25). OCLC 762528287.
33. Sefer Ravid ha-Zahav of Rabbi David Mishreqi (Mizrachi), ed. Shimon Giat, Betar-Ilit 2002, Responsa Ravid Ha-Zahav, responsum # 13, s.v. ונהירנא (p. 182)
34. Babylonian Talmud, Pesahim 12b; 11b
35. Israel Meir Kagan, Mishnah Berura on Shulhan Arukh (Orah Hayyim 261:2:23), otherwise known as the time it takes to walk "three quarters of a biblical mile."
36. In the Babylonian Talmud (Shabbat 118b) we read: Rabbi Jose has said: “Let my portion be with those who usher in the Sabbath day in Tiberias, and with those who dismiss the Sabbath day in Sepphoris.” This has been explained by Aaron Mordechai Freedman (editor of the 1987 Soncino edition of Tractate Shabbath): "In Tiberias, which was situated in a valley, the Sabbath commenced rather earlier, whilst in Sepphoris, which was on a mountain, it terminated rather later than elsewhere." (v. Hebrew-English Edition of the Babylonian Talmud, Tractate Shabbath, Soncino edition, London 1987, s.v. Shabbath 118b, note (b)3).
    
    Freedman's description of twilight being, literally, an oscillating physical reality dependent upon one's location is supported by Rabbi Joseph ibn Migash (1077–1141) and by Rabbi David ben Zimra (c. 1479–1573) , as also by Rabbi Hayyim Eliezer, the son of Isaac ben Moses of Vienna (13th century), who also compiled a book called "Or Zarua" (responsum # 186). Apparently, there is a local phenomenon relating to light emanating from fixed stars in the sky, and their becoming visible once a certain level of darkness has enveloped the land. Rashi, however, differs in view, whose opinion is supported also by Rabbi Menachem Meiri (1249–1306) Langa's Edition, p. 460, and Rabbi Nissim ben Jacob (990–1062), and who all thought that twilight was a fixed time for all, but that the people of Tiberias and Sepphoris were merely stringent in their religious practices, the one group welcoming the Sabbath early, while the other departing from it as late as possible.
37. Tosefot and Tosefot Rash mi-Shantz Pesachim 11b and Tosefot Sanhedrin 41b.
38. Berakhot 2a
39. Berakhot 3a and 27a,
40. Berakhot 26
41. Responsa 1
42. OC 431:1
43. 266
44. Kuntres de-ve shimshei.
45. This is the opinion of Rabbi Nathan Adler (brought by Rabbi Yehosef Schwartz in Divrei Yosef 59b, who himself rejects this opinion), Ben Ish Hai (Year 1 Vayakehel 4:8), Rabbi Mordecai Karmi (Maamar Mordechai 233:2) and others.
46. Mishnah - with a Commentary of Rabbi Moses ben Maimon (ed. Yosef Qafih), vol. 1, Mossad Harav Kook: Jerusalem 1963, s.v. Berakhot 1:5 (p. 33); Megillah 2:4 (p. 232)
47. Responsa of Rabbi David ben Zimra, Book 4, Warsaw 1882 (reprinted), s.v. responsum # 1353 (282)
48. Babylonian Talmud, Shabbat 34b–35a; Chaim Yosef David Azulai, Birkei Yosef (Orah Hayyim, § 261:1), Levorno 1774, citing the author of Ginat Weradim, who wrote: "The world has it as a practice in all the Diaspora communities of Israel the Geonim" (i.e. with respect to the time of bayn ha-shemashot (twilight; nightfall), so that immediately following sunset begins the time known as bayn ha-shemashot, which is the time it takes to walk three quarters of a biblical mile). The opinion of Rabbi Chaim Azulai comes to counter a variant opinion that is also found in the Talmud (Pesahim 94a), where it states that a man is able to walk four mil between sunset and nightfall, an opinion not as widely accepted.
49. Yosef Karo, Shulhan Arukh (Orah Hayyim § 459:2)
50. Divrei Yosef 59b
51. Tukatzinsky, Yechiel Michel (1928). Sefer Bein ha-Shemashos (in Hebrew). Jerusalem. pp. 97-98. OCLC 233065543. The opinion of our Rabbi, the Vilna Gaon, as well as of many other poskim, is that in all the halachic matters touching on the hours , we reckon from sunset until sunset, such as the latest time Kiryat Shema, a quarter of the day (a third of the hours), and the latest time of the prayer, a third of the day (four hours), and the latest time eating leaven on the eve of Passover, a third of the day, and the burning of leaven in another relative hour – all from sunrise until sunset. ...The practice is to be stringent in accordance with the Vilna Gaon's method when it comes to the latest time Kiryat Shema, and the prayer, and when it comes to eating and burning the leaven .{{cite book}}: CS1 maint: location missing publisher (link)
52. Shiurei Tziyon, Siman 35.
53. Minchas Yitzchak, Volume 4, Siman 53
54. Mishnas Rabbi Aharan, Volume 1, Siman 2.
55. Yoma 28b
56. "Zmanim Terms". Kehillat Israel. Archived from the original on 5 June 2015. Retrieved 4 December 2012.
57. Brought in Shu"t Mahara"m Alshaker 96
58. Siddur Rav Saadya Gaon page 26
59. Brought it Mordechai Berakhot #90
60. ^ Beginning of 4th chapter of Berakhot.
61. Teshuva in Peer Hador 44
62. OC 233:1
63. Mishnah - with a Commentary of Rabbi Moses ben Maimon (ed. Yosef Qafih), vol. 1, Mossad Harav Kook: Jerusalem 1963, s.v. Berakhot 1:5 (p. 33)
64. Yosef Karo, Shulhan Arukh (Orah Hayyim § 89:1)
65. Mishnah, Berakhot 4:1 (Maimonides, Mishne Torah, Hil. Tefillah 3:1)
66. Mishnah (Pesahim 1:4)
67. Rabbeinu Hananel's Commentary on Tractate Berakhot (ed. David Metzger), Jerusalem 1990, s.v. Berakhot 26a (p. 51)
68. Josephus, Antiquities (xiv.iv.§ 3)
69. Mishnah, Eduyot 6:1
70. ^ The Mishnah (ed. Herbert Danby), Oxford University Press: Oxford 1977, s.v. Pesahim 5:1, p. 141
71. Josephus, Wars (vi.ix.§ 3)

Notes

• Timekeeping
• Time measurement systems
• Jewish law
• Time in astronomy
• Units of time
• Time in religion
• Jewish law and rituals