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Unequal hours are the division of the light day and the
night Night (also described as night time, unconventionally spelled as "nite") is the period of ambient darkness from sunset Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth's rotation. As view ...
into 12 sections each, whatever the
season A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's tilted orbit around the Sun. In temperate and po ...
. They are also called temporal hours, seasonal hours, biblical or Jewish hours, as well as ancient or Roman hours (). They are ''unequal duration'' periods of time because days are longer and nights shorter in summer than in winter. Their use in everyday life was replaced in the late
Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire ...
by the now common ones of equal duration. The first temporal hour of daylight begins at
Sunrise Sunrise (or sunup) is the moment when the upper rim of the Sun appears on the horizon in the morning. The term can also refer to the entire process of the solar disk crossing the horizon and its accompanying atmospheric effects. Terminology ...
, the first of night at
Sunset Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth's rotation. As viewed from everywhere on Earth (except the North and South poles), the equinox Sun sets due west at the moment of both the spr ...
. For example, if daylight and night are each divided into twelve temporal hours,
Midday Noon (or midday) is 12 o'clock in the daytime. It is written as 12 noon, 12:00 m. (for meridiem, literally 12:00 noon), 12 p.m. (for post meridiem, literally "after noon"), 12 pm, or 12:00 (using a 24-hour clock) or 1200 (military time). Solar ...
and
Midnight Midnight is the transition time from one day to the next – the moment when the date changes, on the local official clock time for any particular jurisdiction. By clock time, midnight is the opposite of noon, differing from it by 12 hours ...
are each the beginning of the seventh hour. A clock that displays the temporal hours is called a temporal clock.


Astronomical basics

To the concept of ''light day'' corresponds the astronomical concept '' Day arc of the Sun''. With the exception of the
equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can al ...
, the duration of daylight depends on the
latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north po ...
and the
season A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's tilted orbit around the Sun. In temperate and po ...
. At 49° north/south latitude (e.g., in
Karlsruhe Karlsruhe ( , , ; South Franconian German, South Franconian: ''Kallsruh'') is the List of cities in Baden-Württemberg by population, third-largest city of the German States of Germany, state (''Land'') of Baden-Württemberg after its capital o ...
), it varies between 16 
equinoctal hour An equinoctial hour is one of the 24 parts of the full day consisting of light day and the night. Its length, unlike the temporal hour, ''does not'' vary with the season, but is constant. The measurement of the full day with equinoctial hours ...
s in summer and 8 equinoctial hours in winter. Due to the continuous change of the duration of daylight over the course of the year, the duration of the day division, i.e. the temporal day hours and the temporal night hours, also changes over the year. The temporal hours of day and night are equal only at the spring and autumn
equinox A solar equinox is a moment in time when the Sun crosses the Earth's equator, which is to say, appears zenith, directly above the equator, rather than north or south of the equator. On the day of the equinox, the Sun appears to rise "due east" ...
es. From 66.5° north/south latitude (
Polar circle A polar circle is a geographic term for a conditional circular line (arc) referring either to the Arctic Circle or the Antarctic Circle. These are two of the keynote circles of latitude (parallels). On Earth, the Arctic Circle is currently ...
s) the sun no longer sets (the
horizon The horizon is the apparent line that separates the surface of a celestial body from its sky when viewed from the perspective of an observer on or near the surface of the relevant body. This line divides all viewing directions based on whether ...
) every day in summer and rises every day in winter. Day does not occur.


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 In biogeography, the Mediterranean Basin (; also known as the Mediterranean Region or sometimes Mediterranea) is the region of lands around the Mediterranean Sea that have mostly a Mediterranean climate, with mild to cool, rainy winters and w ...
from about Classical Greek Antiquity into twelve temporal hours each (). In
Western culture image:Da Vinci Vitruve Luc Viatour.jpg, Leonardo da Vinci's ''Vitruvian Man''. Based on the correlations of ideal Body proportions, human proportions with geometry described by the ancient Roman architect Vitruvius in Book III of his treatise '' ...
they were adopted from the
Roman calendar The Roman calendar was the calendar used by the Roman Kingdom and Roman Republic. The term often includes the Julian calendar established by the reforms of the Roman dictator, dictator Julius Caesar and Roman emperor, emperor Augustus in the ...
and were adopted in the
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located enti ...
an
Medieval In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire a ...
era. They had particular relevance in the fixed daily schedule of the
monastic Monasticism (from Ancient Greek , , from , , 'alone'), also referred to as monachism, or monkhood, is a religious way of life in which one renounces worldly pursuits to devote oneself fully to spiritual work. Monastic life plays an important role ...
orders Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...
. 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). This chronology is used by Jewish religious law (
Halacha ''Halakha'' (; he, הֲלָכָה, ), also transliterated as ''halacha'', ''halakhah'', and ''halocho'' ( ), is the collective body of Jewish religious laws which is derived from the written and Oral Torah. Halakha is based on biblical comm ...
), hence ''
Jewish Jews ( he, יְהוּדִים, , ) or Jewish people are an ethnoreligious group and nation originating from the Israelites Israelite origins and kingdom: "The first act in the long drama of Jewish history is the age of the Israelites""The ...
'' or ''
Biblical The Bible (from Koine Greek , , 'the books') is a collection of religious texts or scriptures that are held to be sacred in Christianity, Judaism, Samaritanism, and many other religions. The Bible is an anthologya compilation of texts of a ...
Division of hours''. Mechanical
clock A clock or a timepiece is a device used to measure and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month and t ...
s encouraged the adoption of equinoctial hours.


Temporal time

For the display of temporal hoursKarlheinz Deußer: ''Temporaluhren: Die Suche nach mechanischen Uhren, die mit Temporalstunden liefen.'' 2012. almost exclusively the
Sundial A sundial is a horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a fl ...
with as hand was once used. The Sun position, which varied throughout the year, served as a parameter on which the varying duration of the temporal hours during the year depended. Many
astronomical clock An astronomical clock, horologium, or orloj is a clock with special mechanisms and dials to display astronomical information, such as the relative positions of the Sun, Moon, zodiacal constellations, and sometimes major planets. Definition ...
s created during the transition to the equal-duration equinoctial hours display temporal hours in addition to the new equal-duration hours. Even where temporal hours continued to be used (especially in monasteries), the mechanical clock was used. This required two different settings for the day and for the night, or one clock each for the day and the night. For the latter, the speed of the Waag was changed, for example, in 26 steps (i.e., half the numerical value of 52 weeks). In the weeks of the
Equinox A solar equinox is a moment in time when the Sun crosses the Earth's equator, which is to say, appears zenith, directly above the equator, rather than north or south of the equator. On the day of the equinox, the Sun appears to rise "due east" ...
, both clocks could be operated with the middle weight position on the balance.


See also

*
Twilight Twilight is light produced by sunlight scattering in the upper atmosphere, when the Sun is below the horizon, which illuminates the lower atmosphere and the Earth's surface. The word twilight can also refer to the periods of time when this ...
*
Terminator (solar) A terminator or twilight zone is a moving line that divides the daylit side and the dark night side of a planetary body. The terminator is defined as the locus of points on a planet or moon where the line through the center of its parent star ...
* (in German) *
Time perception The study of time perception or chronoception is a field within psychology, cognitive linguistics and neuroscience that refers to the subjective experience, or sense, of time, which is measured by someone's own perception of the duration of the ind ...
*
Civil time In modern usage, civil time refers to statutory time as designated by civilian authorities. Modern civil time is generally national standard time in a time zone at a fixed offset from Coordinated Universal Time (UTC), possibly adjusted by daylig ...
* equinoctial hours * * Danna *
Julian day The Julian day is the continuous count of days since the beginning of the Julian period, and is used primarily by astronomers, and in software for easily calculating elapsed days between two events (e.g. food production date and sell by date). ...
*
Chronobiology Chronobiology is a field of biology that examines Time, timing processes, including periodic (cyclic) phenomena in living organisms, such as their adaptation to sun, solar- and moon, lunar-related rhythms. These cycles are known as biological rh ...
* {{Ill, Ancient Egyptian Day, de, Tag_(Altes_Ägypten)


Bibliography

* 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.


References


External links


Die Temporalstunden
Jewish law Timekeeping Pages with unreviewed translations History of timekeeping