Relative hour

Relative hour (

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,^[6] and with sunrise according to others.^[7] 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.^[8] 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

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).

The earliest reference to the use of temporal hours in Jewish literature comes from Abraham bar Hiyya, and, later, elaborated further by Maimonides.

Jewish tradition

The prevailing opinion is that each day begins at the rise of dawn (Heb. עלות השחר‎),^{[9][10][11][12][13]} which is about 72 minutes before sunrise,^[14] yet, for practical reasons in some biblically related commandments, some scholars begin counting the hours of the day from sunrise (Heb. הנץ החמה‎),^[15][16][17] 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,^[18][19][20] 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.^[21]

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.^[22]

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."^[23][24] 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.^{[25][26][27][28][29]} Rabbeinu Tam, disputing, held the time of bayn ha-sh'meshot to be 58.5 minutes.^[30]

Disputations

In old times, the hour was detected by observation of the position of the sun,

• 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,^[35] the Rashba,^[36] the Ritva,^[37] the Ra'ah,^[38] the Terumat ha-deshen,^[39] the Bach,^[40] the Eliyah Rabba,^[41] and the Pri Chadash^[42]
  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
  Maran's Shulhan Arukh, a man traverses a biblical mile in 18 minutes,^[47] 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,^[48] Rabbi Yechiel Michel Tucazinsky,^[49] Rabbi Avraham Chaim Naeh,^[50] Rabbi Yitzchok Yaakov Weiss,^[51] Rabbi Aharon Kotler^[52] 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^[53]
  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.^[54] This is also the opinion of Rav Nisim Gaon,^[55] Rav Saadya Gaon,^[56] Rav Hai Gaon,^[57] Rabbeinu Chananel,^[58] Maimonides,^[59] Rabbeinu Yonah,^[58] and the Levush.^[60] In Roman times, these daylight hours were known as unequal hours.

In the

• 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
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