Ab urbe condita
Ab urbe condita, or Anno urbis conditæ abbreviated as AUC in either case, is a convention, used in antiquity and by classical historians to refer to a given year in Ancient Rome. Ab urbe condita means "from the founding of the City," while anno urbis conditæ means "in the year since the City's founding." Therefore, the traditional year of the foundation of Rome, 753 BC, would be written AUC 1, while AD 1 would be AUC 754. The foundation of the Empire in 27 BC would be AUC 727. Usage of the term was more common during the Renaissance, when editors sometimes added AUC to Roman manuscripts they published, giving the false impression that the convention was used in antiquity. In reality, the dominant method of identifying years in Roman times was to name the two consuls who held office that year. In late antiquity, regnal years were in use, as was the Diocletian era in Roman Egypt after AD 293, in the Byzantine Empire after AD 537, following a decree by Justinian; the traditional date for the founding of Rome, 21 April 753 BC, is due to Marcus Terentius Varro.
Varro may have used the consular list and called the year of the first consuls "ab urbe condita 245," accepting the 244-year interval from Dionysius of Halicarnassus for the kings after the foundation of Rome. The correctness of this calculation has not been confirmed. From the time of Claudius onward, this calculation superseded other contemporary calculations. Celebrating the anniversary of the city became part of imperial propaganda. Claudius was the first to hold magnificent celebrations in honor of the anniversary of the city, in AD 48, the eight hundredth year from the founding of the city. Hadrian and Antoninus Pius held similar celebrations, in AD 121, in AD 147 and AD 148, respectively. In AD 248, Philip the Arab celebrated Rome's first millennium, together with Ludi saeculares for Rome's alleged tenth sæculum. Coins from his reign commemorate the celebrations. A coin by a contender for the imperial throne, explicitly states "ear one thousand and first", an indication that the citizens of the empire had a sense of the beginning of a new era, a Sæculum Novum.
The Anno Domini year numbering was developed by a monk named Dionysius Exiguus in Rome in AD 525, as a result of his work on calculating the date of Easter. Dionysius did not use the AUC convention, but instead based his calculations on the Diocletian era; this convention had been in use since AD 293, the year of the tetrarchy, as it became impractical to use regnal years of the current emperor. In his Easter table, the year AD 532 was equated with the 248th regnal year of Diocletian; the table counted the years starting from the presumed birth of Christ, rather than the accession of the emperor Diocletian on 20 November AD 284, or as stated by Dionysius: "sed magis elegimus ab incarnatione Domini nostri Jesu Christi annorum tempora praenotare". Blackburn and Holford-Strevens review interpretations of Dionysius which place the Incarnation in 2 BC, 1 BC, or AD 1, it has been calculated that the year AD 1 corresponds to AUC 754, based on the epoch of Varro. Thus, AUC 1 = 753 BC AUC 753 = 1 BC AUC 754 = AD 1 AUC 1000 = AD 247 AUC 1229 = AD 476 AUC 2206 = AD 1453 AUC 2753 = AD 2000 AUC 2772 = AD 2019 List of Latin phrases
The traditional China calendar, or Former Calendar, Traditional Calendar or Lunar Calendar, is a lunisolar calendar which reckons years and days according to astronomical phenomena. It is defined by GB/T 33661-2017, "Calculation and promulgation of the Chinese calendar", issued by the Standardisation Administration of China on 12 May 2017. Although modern day China uses the Gregorian calendar, the traditional Chinese calendar governs holidays in China and in overseas Chinese communities, it lists the dates of traditional Chinese holidays and guides people in selecting auspicious days for weddings, moving, or starting a business. Like Chinese characters, variants of this calendar are used in different parts of the Chinese cultural sphere. Korea and the Ryukyu Islands adopted the calendar, it evolved into Korean and Ryukyuan calendars; the main difference from the traditional Chinese calendar is the use of different meridians, which leads to some astronomical events—and calendar events based on them—falling on different dates.
The traditional Japanese calendar derived from the Chinese calendar, but its official use in Japan was abolished in 1873 as part of reforms after the Meiji Restoration. Calendars in Mongolia and Tibet have absorbed elements of the traditional Chinese calendar, but are not direct descendants of it. Days begin and end at midnight, months begin on the day of the new moon. Years begin on the second new moon after the winter solstice. Solar terms govern the end of each month. Written versions in ancient China included stems and branches of the year and the names of each month, including leap months as needed. Characters indicated whether a month was short; the traditional Chinese calendar was developed between 771 and 476 BC, during the Spring and Autumn period of the Eastern Zhou dynasty. Before the Zhou dynasty, solar calendars were used. One version of the solar calendar is the five-elements calendar. A 365-day year was divided into five phases of 73 days, with each phase corresponding to a Day 1 Wu Xing element.
A phase began followed by six 12-day weeks. Each phase consisted of two three-week months. Years began followed by a bǐngzǐ day and a 72-day fire phase. Other days were tracked using the Yellow River Map. Another version is a four-quarters calendar. Weeks were ten days long, with one month consisting of three weeks. A year had 12 months, with a ten-day week intercalated in summer as needed to keep up with the tropical year; the 10 Heavenly Stems and 12 Earthly Branches were used to mark days. A third version is the balanced calendar. A year was 365.25 days, a month was 29.5 days. After every 16th month, a half-month was intercalated. According to oracle bone records, the Shang dynasty calendar was a balanced calendar with 12 to 14 months in a year; the first lunisolar calendar was the Zhou calendar, introduced under the Zhou dynasty. This calendar set the beginning of the year at the day of the new moon before the winter solstice, it set the shàngyuán as the winter solstice of a dīngsì year, making the year it was introduced around 2,758,130.
Several competing lunisolar calendars were introduced by states fighting Zhou control during the Warring States period. The state of Lu issued its own Lu calendar. Jin issued the Xia calendar in AD 102, with a year beginning on the day of the new moon nearest the March equinox. Qin issued the Zhuanxu calendar, with a year beginning on the day of the new moon nearest the winter solstice. Song's Yin calendar began its year on the day of the new moon after the winter solstice; these calendars are known as the six ancient calendars, or quarter-remainder calendars, since all calculate a year as 365 1⁄4 days long. Months begin on the day of the new moon, a year has 12 or 13 months. Intercalary months are added to the end of the year; the Qiang and Dai calendars are modern versions of the Zhuanxu calendar, used by mountain peoples. After Qin Shi Huang unified China under the Qin dynasty in 221 BC, the Qin calendar was introduced, it followed most of the rules governing the Zhuanxu calendar, but the month order was that of the Xia calendar.
The intercalary month, known as the second Jiǔyuè, was placed at the end of the year. The Qin calendar was used into the Han dynasty. Emperor Wu of Han r. 141 – 87 BC introduced reforms halfway through his reign. His Taichu Calendar defined a solar year as 365 385⁄1539 days, the lunar month was 29 43⁄81 days; this calendar introduced the 24 solar terms. Solar terms were paired, with the 12 combined periods known as climate terms; the first solar term of the period was known as a pre-climate, the second was a mid-climate. Months were named for the mid-climat
The 3rd century was the period from 201 to 300 A. D. or C. E. In this century, the Roman Empire saw a crisis, starting with the assassination of the Roman Emperor Severus Alexander in 235, plunging the empire into a period of economic troubles, barbarian incursions, political upheavals, civil wars, the split of the Roman Empire through the Gallic Empire in the west and the Palmyrene Empire in the east, which all together threatened to destroy the Roman Empire in its entirety, but the reconquests of the seceded territories by Emperor Aurelian and the stabilization period under Emperor Diocletian due to the administrative strengthening of the empire caused an end to the crisis by 284; this crisis would mark the beginning of Late Antiquity. In Persia, the Parthian Empire was succeeded by the Sassanid Empire in 224 after Ardashir I defeated and killed Artabanus V during the Battle of Hormozdgan; the Sassanids went on to subjugate many of the western portions of the declining Kushan Empire. In China, the chaos, raging since 189 would continue to persist with the decisive defeat of Cao Cao at the Battle of Red Cliffs in 208, which would end the hopes of unification and lead to the tripartite division of China into three main empires.
In India, the Gupta Empire was on the rise towards the end of the century. Korea was ruled by the Three Kingdoms of Korea. Japan entered the Kofun period; the Xiongnu formed the Tiefu state under Liu Qubei. The Southeast Asian mainland was dominated by Funan. At about this time in Sub-Saharan Africa, the Bantu expansion reached Southern Africa. In Pre-Columbian America, the Adena culture of the Ohio River valley declined in favor of the Hopewell culture; the Maya civilization entered its Classic Era. After the death of Commodus in the late previous century the Roman Empire was plunged into a civil war; when the dust settled, Septimius Severus emerged as emperor. Unlike previous emperors, he used the army to back his authority, paid them well to do so; the regime he created is known as the Military Monarchy as a result. The system fell apart in the 230s, giving way to a fifty-year period known as the Military Anarchy or the Crisis of the Third Century, following the assassination of the 28-year-old emperor Severus Alexander, where no fewer than twenty emperors held the reins of power, most for only a few months.
The majority of these men were assassinated, or killed in battle, the empire collapsed under the weight of the political upheaval, as well as the growing Persian threat in the east. Under its new Sassanid rulers, Persia had grown into a rival superpower, the Romans would have to make drastic reforms in order to better prepare their state for a confrontation; these reforms were realized late in the century under the reign of Diocletian, one of them being to divide the empire into an eastern and western half, have a separate ruler for each. Early 3rd century – Burial in catacombs becomes common place. 208: the Chinese naval Battle of Red Cliffs occurs. 211 – 217: Caracalla, Roman Emperor. 212: Constitutio Antoniniana grants citizenship to all free Roman men. 212 – 217: Baths of Caracalla. 220: The Han Dynasty comes to an end with establishment of the Three Kingdoms in ancient China. 220 – 280: The Three Kingdoms period. 222 – 235: Alexander Severus, Roman Emperor. 224: Ardashir I of the Sassanid dynasty conquers the Parthian empire at the Battle of Hormozdgān.
230 – 232: Sassanid dynasty of Persia launches a war to reconquer lost lands in the Roman east. 234: Zhuge Liang dies of illness at the standoff of Wuzhang Plains. 235 – 284: Crisis of the Third Century shakes Roman Empire. 241: The Kingdom of Araba dissolved after the Fall of Hatra to Persia 244: Battle of Xingshi in China. 250 – 538: Kofun era, the first part of the Kofun period in Japan. 258: Valerian's massacre of Christians. 260: Roman Emperor Valerian I is taken captive by Shapur I of Persia. 263: Cao Wei conquers the Shu Han Kingdom. 266: The Jin Dynasty is founded after the overthrow of the Cao Wei Dynasty by Sima Yan. 280: The Jin Dynasty reunites China under one empire after the conquest of Eastern Wu. 284 – 305: Diocletian, Roman Emperor. 291 – 306: The War of the Eight Princes, a civil war by the Sima Clan in China. Sarnath becomes a center of Buddhist arts in India. Diffusion of maize as a food crop from Mexico into North America begins; the Kingdom of Funan reaches its zenith. The Goths move from Gothiscandza to Ukraine.
Menorahs and Ark of the Covenant, wall painting in a Jewish catacomb, Villa Torlonia, are made. The Coptic period begins. Siddhartha in the Palace, detail of a relief from Nagarjunakonda, Andhra Pradesh, India, is made. Andhra period; the artwork is now kept at New Delhi. Jonah Swallowed and Jonah Cast Up, two statuettes of a group from the eastern Mediterranean Asia Minor, are made. Now kept at The Cleveland Museum of Art; the Magerius Mosaic is made. Late 3rd century-early 4th century – Good Shepherd and Story of Jonah, painted ceiling of the Catacombs of Marcellinus and Peter in Rome, is made. Ardashir I, founder of the Sasanid Empire Artabanus V, last ruler of the Parthian Empire Aurelian, Roman emperor Clement of Alexandria, Christian head of Catechetical School of Alexandria Cao Ca
The 2nd century is the period from 101 to 200 in accordance with the Julian calendar in the Common Era. It is considered part of epoch, or historical period. Early in the century, the Roman Empire attained its greatest expansion under the emperor Trajan, but after his death became defensive for the rest of its history. Much prosperity took place throughout the empire at this time, ruled as it were by the Five Good Emperors, a succession of well-received and able rulers; this period saw the removal of the Jews from Jerusalem during the reign of Hadrian after Bar Kokhba's revolt. The last quarter of the century saw the end of the period of peace and prosperity known as the Pax Romana at the death of the emperor Marcus Aurelius, last of the "Five Good Emperors", the ascension of Commodus. After Commodus was murdered in 192, a turbulent period known as the Year of the Five Emperors ensued, after the quick successive removals of Pertinax and Didius Julianus from power, had the general-turned-emperor Septimius Severus, founder of the Severan dynasty, pitted against rival claimants in the form of Pescennius Niger, whom his forces defeated at the Battle of Issus in 194, Clodius Albinus, whom he defeated at the Battle of Lugdunum in 197, granting him sole authority over the empire.
Although the Han Dynasty of China was cemented into power and extended its imperial influence into Central Asia during the first half of the century, by the second half there was widespread corruption and open rebellion. This set in motion its ultimate decline, in September 189, the Han general Dong Zhuo, after being summoned to the capital by He Jin to help quell the corrupt and powerful eunuch faction by serving as an intimidator to both them and the Empress Dowager, marched his army into Luoyang in light of He Jin's assassination and the subsequent slaughter of the eunuchs, taking over the capital and becoming the de facto head of the government, although warlords and government officials took against him in a campaign that, while failing to put him down, compelled Dong Zhuo to shift the seat of imperial power further west to Chang'an; as Dong Zhuo was killed in 192, the chaos in the wake of the collapse of centralized authority only continued, with various warlords attempting to vye for supremacy in order to establish or hold onto their authority within the decaying empire.
Meanwhile, Dong Zhuo's former followers Li Jue and Guo Si were left to squabble amongst themselves, while the emperor himself fled and returned to the ravaged city of Luoyang, but shortly thereafter, in 196, was given refuge by the warlord Cao Cao, who relocated him to the new capital city of Xu, from where Cao Cao could control the emperor. Cao Cao would only further exert his authority by defeating the powerful warlord Yuan Shao at the decisive Battle of Guandu in 200. AD 96 – 180: Five Good Emperors of Rome: Nerva, Hadrian, Antoninus Pius, Marcus Aurelius. 100 - 200: The Grand Anicut an ancient dam is constructed by a Chola king. The Kingdom of Aksum emerges. 101 – 102, 105 – 106: The Dacian Wars. After two conflicts, Dacia is annexed as a Roman province. 114 – 116: A war with Parthia results in Armenia and Mesopotamia being temporarily annexed into the Roman Empire. 115 – 117: Kitos War, adjunct to the Jewish–Roman wars. 122 – 132: Hadrian's Wall across Northern England. 127 – 140: Kanishka, Kushan Ruler.
132 – 135: Bar Kokhba's revolt against Rome. 132: Chinese chronicles described the existence of diplomatic relations between Java and China. 140 – 180: Huvishka, Kushan ruler. 142 – 154: The Antonine Wall is built across central Scotland. 144: Marcion, rejected by Church of Rome, founds Marcionism. 161 – 166: Roman–Parthian War of 161–166. 165 – 180: The Antonine Plague in Rome. 166 – 180: Marcomannic Wars. 166 – 184: Disasters of the Partisan Prohibitions. 180 – 192: Commodus, Roman Emperor. 184 – 205: The Yellow Turban Rebellion of the Han Dynasty in China begins. 184 – 189: The Liang Province Rebellion breakouts in Northwest China. 189 – 220: The End of the Han dynasty. 190 – 191: Warlords across China launches a Campaign against Dong Zhuo. 193: Roman Year of the Five Emperors. 193 – 211: Septimius Severus, Roman Emperor. Herakleitos makes The Unswept Floor, mosaic variant of a 2nd-century BC painting by Sosos of Pergamon, it is now kept in Rome. C. 2nd or 3rd century – Standing Buddha, from Gandhara, is made.
Kushan period. It is now kept at Lahore. Antoninus Pius, Roman Emperor Cai Yong, Chinese scholar Commodus, Roman Emperor Dong Zhuo, Chinese general and warlord Hadrian, Roman Emperor Huvishka, Kushan Ruler Ignatius, third bishop of Antioch, author of letters Irenaeus, second bishop of Lyon, author of Against the Heresies Julia Domna, Empress of Rome Justin Martyr, Christian apologist Kanishka, Kushan ruler Karikala, King of the Chola dynasty who constructed the Grand Anicut dam for farmers in Tamilnadu Kong Rong, Chinese scholar Lü Bu, Chinese general and warlord Lucius Verus, Roman Emperor Marcus Aurelius, Roman Emperor, philosopher Montanus, Christian heretic. Nagarjuna, founder of Madhyamaka Buddhism Polycarp, bishop of Smyrna. Rabbi Akiva, Head of the Jewish Sages Rabbi Yehuda haNasi, redactor of the Mishnah Septimius Severus, Roman Emperor Simon bar Kokhba, Jewish rebel leader Sun Ce, Chinese general and warlord Trajan, Roman Emperor Victor I, bishop of Rome. Vologases IV, Parthian ruler Vologases V, Parthian ruler Wang Yun, Chinese official Qiao Xuan, Chinese official Yuan Shao, Chinese warlord Yuan Shu, Chinese warlord Zhang Daoling, Chinese Taoist hermit.
Zhang Heng, Chinese statesman, inventor, astronomer and engineer. Zhang Jue, Chinese rebel leader Zhang Zhongjing, one of the most famous Chinese physicians during Han Dynasty. Achilles Tatius
The Horse is the seventh of the 12-year cycle of animals which appear in the Chinese zodiac related to the Chinese calendar. There is a long tradition of the Horse in Chinese mythology. Certain characteristics of the Horse nature are supposed to be typical of or to be associated with either a year of the Horse and its events, or in regard to the personality of someone born in such a year. Horse aspects can enter by other chronomantic factors or measures, such as hourly. People born within these date ranges can be said to have been born in the "Year of the Horse", while bearing the following elemental sign: Horse Chinese astrology Chinese New Year Burmese zodiac Horse worship Hale, Jill; the Practical Encyclopedia of Feng Shui. New York: Barnes and Noble Books. ISBN 0-7607-3741-X
The Islamic, Muslim, or Hijri calendar is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to determine the proper days of Islamic holidays and rituals, such as the annual period of fasting and the proper time for the pilgrimage to Mecca; the civil calendar of all countries where the religion is predominantly Muslim is the Gregorian calendar. Notable exceptions to this rule are Afghanistan, which use the Solar Hijri calendar. Rents and similar regular commitments are paid by the civil calendar; the Islamic calendar employs the Hijri era whose epoch was established as the Islamic New Year of 622 AD/CE. During that year and his followers migrated from Mecca to Yathrib and established the first Muslim community, an event commemorated as the Hijra. In the West, dates in this era are denoted AH in parallel with the Christian and Jewish eras. In Muslim countries, it is sometimes denoted as H from its Arabic form. In English, years prior to the Hijra are reckoned as BH.
The current Islamic year is 1440 AH. In the Gregorian calendar, 1440 AH runs from 11 September 2018 to 30 August 2019. For central Arabia Mecca, there is a lack of epigraphical evidence but details are found in the writings of Muslim authors of the Abbasid era. Inscriptions of the ancient South Arabian calendars reveal the use of a number of local calendars. At least some of these South Arabian calendars followed the lunisolar system. Both al-Biruni and al-Mas'udi suggest that the ancient Arabs used the same month names as the Muslims, though they record other month names used by the pre-Islamic Arabs; the Islamic tradition is unanimous in stating that Arabs of Tihamah and Najd distinguished between two types of months and forbidden months. The forbidden months were four months during which fighting is forbidden, listed as Rajab and the three months around the pilgrimage season, Dhu al-Qa‘dah, Dhu al-Hijjah, Muharram. Information about the forbidden months is found in the writings of Procopius, where he describes an armistice with the Eastern Arabs of the Lakhmid al-Mundhir which happened in the summer of 541 AD/CE.
However, Muslim historians do not link these months to a particular season. The Qur'an links the four forbidden months with Nasī’, a word that means "postponement". According to Muslim tradition, the decision of postponement was administered by the tribe of Kinanah, by a man known as the al-Qalammas of Kinanah and his descendants. Different interpretations of the concept of Nasī’ have been proposed; some scholars, both Muslim and Western, maintain that the pre-Islamic calendar used in central Arabia was a purely lunar calendar similar to the modern Islamic calendar. According to this view, Nasī’ is related to the pre-Islamic practices of the Meccan Arabs, where they would alter the distribution of the forbidden months within a given year without implying a calendar manipulation; this interpretation is supported by Arab historians and lexicographers, like Ibn Hisham, Ibn Manzur, the corpus of Qur'anic exegesis. This is corroborated by an early Sabaic inscription, where a religious ritual was "postponed" due to war.
According to the context of this inscription, the verb ns'’ has nothing to do with intercalation, but only with moving religious events within the calendar itself. The similarity between the religious concept of this ancient inscription and the Qur'an suggests that non-calendaring postponement is the Qur'anic meaning of Nasī’; the Encyclopaedia of Islam concludes "The Arabic system of can only have been intended to move the Hajj and the fairs associated with it in the vicinity of Mecca to a suitable season of the year. It was not intended to establish a fixed calendar to be observed." The term "fixed calendar" is understood to refer to the non-intercalated calendar. Others concur that it was a lunar calendar, but suggest that about 200 years before the Hijra it was transformed into a lunisolar calendar containing an intercalary month added from time to time to keep the pilgrimage within the season of the year when merchandise was most abundant; this interpretation was first proposed by the medieval Muslim astrologer and astronomer Abu Ma'shar al-Balkhi, by al-Biruni, al-Mas'udi, some western scholars.
This interpretation considers Nasī’ to be a synonym to the Arabic word for "intercalation". The Arabs, according to one explanation mentioned by Abu Ma'shar, learned of this type of intercalation from the Jews; the Jewish Nasi was the official. Some sources say that the Arabs followed the Jewish practice and intercalated seven months over nineteen years, or else that they intercalated nine months over 24 years. Postponement of one ritual in a particular circumstance does not imply alteration of the sequence of months, scholars agree that this did not happen. Al-Biruni says this did not happen, the festivals were kept within their season by intercalation every second or third year of a month between Dhu al-Hijjah and Muharram, he says that, in terms of the fixed calendar, not introduced until 10 AH, the first intercalation was, for example, of a month between Dhu al-Hijjah and Muharram, the second of a month between Muharram and Safar, the third of a month between Safar and Rabi'I, so on. The intercalations were arranged.
The notice of interca
The Hebrew or Jewish calendar is a lunisolar calendar used today predominantly for Jewish religious observances. It determines the dates for Jewish holidays and the appropriate public reading of Torah portions and daily Psalm readings, among many ceremonial uses. In Israel, it is used for religious purposes, provides a time frame for agriculture and is an official calendar for civil purposes, although the latter usage has been declining in favor of the Gregorian calendar; the present Hebrew calendar is the product including a Babylonian influence. Until the Tannaitic period, the calendar employed a new crescent moon, with an additional month added every two or three years to correct for the difference between twelve lunar months and the solar year; the year in which it was added was based on observation of natural agriculture-related events in ancient Israel. Through the Amoraic period and into the Geonic period, this system was displaced by the mathematical rules used today; the principles and rules were codified by Maimonides in the Mishneh Torah in the 12th century.
Maimonides' work replaced counting "years since the destruction of the Temple" with the modern creation-era Anno Mundi. The Hebrew lunar year is about eleven days shorter than the solar year and uses the 19-year Metonic cycle to bring it into line with the solar year, with the addition of an intercalary month every two or three years, for a total of seven times per 19 years. With this intercalation, the average Hebrew calendar year is longer by about 6 minutes and 40 seconds than the current mean tropical year, so that every 217 years the Hebrew calendar will fall a day behind the current mean tropical year; the era used. As with Anno Domini, the words or abbreviation for Anno Mundi for the era should properly precede the date rather than follow it. AM 5779 began at sunset on 9 September 2018 and will end at sunset on 29 September 2019; the Jewish day is of no fixed length. The Jewish day is modeled on the reference to "...there was evening and there was morning..." in the creation account in the first chapter of Genesis.
Based on the classic rabbinic interpretation of this text, a day in the rabbinic Hebrew calendar runs from sunset to the next sunset. Halachically, a day ends and a new one starts when three stars are visible in the sky; the time between true sunset and the time when the three stars are visible is known as'bein hashmashot', there are differences of opinion as to which day it falls into for some uses. This may be relevant, for example, in determining the date of birth of a child born during that gap. There is no clock in the Jewish scheme. Though the civil clock, including the one in use in Israel, incorporates local adoptions of various conventions such as time zones, standard times and daylight saving, these have no place in the Jewish scheme; the civil clock is used only as a reference point – in expressions such as: "Shabbat starts at...". The steady progression of sunset around the world and seasonal changes results in gradual civil time changes from one day to the next based on observable astronomical phenomena and not on man-made laws and conventions.
In Judaism, an hour is defined as 1/12 of the time from sunrise to sunset, so, during the winter, an hour can be much less than 60 minutes, during the summer, it can be much more than 60 minutes. This proportional hour is known as a sha'ah z'manit. A Jewish hour is divided into parts. A part is 1/18 minute; the ultimate ancestor of the helek was a small Babylonian time period called a barleycorn, itself equal to 1/72 of a Babylonian time degree. These measures are not used for everyday purposes. Instead of the international date line convention, there are varying opinions as to where the day changes. One opinion uses the antimeridian of Jerusalem. Other opinions exist as well; the weekdays proceed to Saturday, Shabbat. Since some calculations use division, a remainder of 0 signifies Saturday. While calculations of days and years are based on fixed hours equal to 1/24 of a day, the beginning of each halachic day is based on the local time of sunset; the end of the Shabbat and other Jewish holidays is based on nightfall which occurs some amount of time 42 to 72 minutes, after sunset.
According to Maimonides, nightfall occurs. By the 17th century, this had become three-second-magnitude stars; the modern definition is when the center of the sun is 7° below the geometric horizon, somewhat than civil twilight at 6°. The beginning of the daytime portion of each day is determined both by sunrise. Most halachic times are based on some combination of these four times and vary from day to day throughout the year and vary depending on location; the daytime hours are divided into Sha'oth Zemaniyoth or "Halachic hours" by taking the time between sunrise and sunset or between dawn and nightfall and dividing it into 12 equal hours. The nighttime hours are s