Relative hour (Hebrew singular: / ; plural: / ), 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.Yaakov de Castro, `Erekh Leḥem (Orach Chaim §233:2) 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,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. and with sunrise according to others.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. 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 () and fall () equinoxes (around 20 March and 23 September), the length of a day and night are equal.Jerusalem Talmud (Berakhot 1:1) However, even during the summer and winter solstices 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 ().
In Western culture they were adopted from Roman timekeeping 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).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, ; Rudolf Wendorff: Zeit und Kultur. Geschichte des Zeitbewusstseins in Europa. Westdeutscher Vlg, Wiesbaden 1980,
Jewish tradition The prevailing opinion is that each day begins at the rise of dawn (Heb. ),Babylonian Talmud, Berakhot 59b, Rashi s.v. שבתאי; Mishnah Berakhot 1:1Babylonian Talmud, Megillah 20a, Rashi, s.v. עד הנץ החמהMagen Avraham on Shulchan Aruch (Orach Chayim §58:1) 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. ),Mordecai Yoffe, Levush Malkhus (Orach Chayim, sections 233:1, 266)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. 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,Maimonides, Mishneh Torah (Hil. Kiryat Shema 1:10–13)Shulchan Aruch (Orach Chayim 58:1) 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.Babylonian Talmud, Pesahim 12b; , a facsimile, printed from the first Venice edition (MS. 1546)
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 [stars] is a doubtful case; three [stars] is certainly night.Jerusalem Talmud (Berakhot 1:1 [2b])
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 [below the horizon] until there appear [in the sky] three medium-sized stars." (reprinted in 1988) 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.Babylonian Talmud (Shabbat 34b–35a); cf. Moses Alashkar, Responsa (responsum # 96), Sabbionetta, 1553; ; Yaakov de Castro, Erekh Lehem (Orach Chayim, section 260:2); Isaac of Corbeil (Sefer Mitzvot Ḳatan); , s.v. part IV, responsum # 1353 (reprinted in Israel, n.d.) 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 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,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) 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).Babylonian Talmud, Pesahim 12b; 11b 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.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." Typically, nightfall ushers in more quickly in the low-lying valleys, than it does on a high mountaintop.In the Babylonian Talmud (Shabbat 118b) we read: Rabbi Jose has said: “Let my portion be with those who usher in the Sabbath day [at its outset] in Tiberias, and with those who dismiss the Sabbath day [at its recess] 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) [Responsa of R. Joseph ibn Migash, responsum # 45] and by Rabbi David ben Zimra (c. 1479–1573) [Responsa of Rabbi David ben Zimra, book I, responsum # 76], 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.
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 () 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,Tosefot and Tosefot Rash mi-Shantz Pesachim 11b and Tosefot Sanhedrin 41b. the Rashba,Berakhot 2a the Ritva,Berakhot 3a and 27a, the Ra'ah,Berakhot 26 the Terumat ha-deshen,Responsa 1 the Bach,OC 431:1 the Eliyah Rabba,266 and the Pri ChadashKuntres de-ve shimshei. 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).