An Olympiad is a period of four years associated with the Olympic Games of the Ancient Greeks. Although the Ancient Olympic Games were established during Archaic Greece, it was not until the Hellenistic period, beginning with Ephorus, that the Olympiad was used as a calendar epoch. Converting to the modern BC/AD dating system the first Olympiad began in the summer of 776 BC and lasted until the summer of 772 BC, when the second Olympiad would begin with the commencement of the next games. By extrapolation to the Gregorian calendar, the 3rd year of the 699th Olympiad will begin in mid-summer 2019. A modern Olympiad refers to a four-year period beginning on the opening of the Olympic Games for the summer sports; the first modern Olympiad began in 1896, the second in 1900, so on. The ancient and modern Olympiads would have synchronised had there been a year zero between the Olympiad of 4 BC and the one of 4 AD, but as the Gregorian calendar goes directly from 1 BC to 1 AD, the ancient Olympic cycle now lags the modern cycle by one year.
An ancient Olympiad was a period of four years grouped together, counting inclusively as the ancients did. Each ancient Olympic year overlapped onto two of our modern reckoning of BC or AD years, from midsummer to midsummer. Example: Olympiad 140, year 1 = 220/219 BC. Therefore, the games would have been held in July/August of 220 BC and held the next time in July/August of 216 BC, after four olympic years had been completed; the sophist Hippias was the first writer to publish a list of victors of the Olympic Games, by the time of Eratosthenes, it was agreed that the first Olympic games had happened during the summer of 776 BC. The combination of victor lists and calculations from 776 BC onwards enabled Greek historians to use the Olympiads as a way of reckoning time that did not depend on the time reckonings of one of the city-states; the first to do so was Timaeus of Tauromenium in the third century BC. Since for events of the early history of the games the reckoning was used in retrospect, some of the dates given by historian for events before the 5th century BC are unreliable.
In the 2nd century AD, Phlegon of Tralles summarised the events of each Olympiad in a book called Olympiads, an extract from this has been preserved by the Byzantine writer Photius. Christian chroniclers continued to use this Greek system of dating as a way of synchronising biblical events with Greek and Roman history. In the 3rd century AD, Sextus Julius Africanus compiled a list of Olympic victors up to 217 BC, this list has been preserved in the Chronicle of Eusebius. Early historians sometimes used the names of Olympic victors as a method of dating events to a specific year. For instance, Thucydides says in his account of the year 428 BC: "It was the Olympiad in which the Rhodian Dorieus gained his second victory". Dionysius of Halicarnassus dates the foundation of Rome to the first year of the seventh Olympiad, 752/1 BC. Since Rome was founded on April 21, in the last half of the ancient Olympic year, it would be 751 BC specifically. In Book 1 chapter 75 Dionysius states: "... Romulus, the first ruler of the city, began his reign in the first year of the seventh Olympiad, when Charops at Athens was in the first year of his ten-year term as archon."
Diodorus Siculus dates the Persian invasion of Greece to 480 BC: "Calliades was archon in Athens, the Romans made Spurius Cassius and Proculus Verginius Tricostus consuls, the Eleians celebrated the Seventy-fifth Olympiad, that in which Astylus of Syracuse won the stadion. It was in this year that king Xerxes made his campaign against Greece." Jerome, in his Latin translation of the Chronicle of Eusebius, dates the birth of Jesus Christ to year 3 of Olympiad 194, the 42nd year of the reign of the emperor Augustus, which equates to the year 2 BC. An Olympiad started with the holding of the games, which occurred on the first or second full moon after the summer solstice, in what we call July or August; the games were therefore a new years festival. In 776 BC this occurred on either July 23 or August 21.. Though the games were held without interruption, on more than one occasion they were held by others than the Eleians; the Eleians declared such games Anolympiads, but it is assumed the winners were recorded.
During the 3rd century AD, records of the games are so scanty that historians are not certain whether after 261 they were still held every four years. During the early years of the Olympiad, any physical benefit deriving from a sport was banned; some winners were recorded though, until the last Olympiad of 393AD. In 394, Roman Emperor Theodosius. Though it would have been possible to continue the reckoning by just counting four-year periods, by the middle of the 5th century AD reckoning by Olympiads had become disused; the modern Olympiad is a period of four years, beginning at the opening of the Olympic Summer Games and ending at the opening of the next. The Olympiads are numbered consecutively from the first Games of the Olympiad celebrated in Athens in 1896; the XXXI Olympiad began on August 5, 2016 and will end on July 24, 2020. The Summer Olympics are more referred to as the Games of the Olympiad; the first poster to announce the games using this term was the one for the 1932 Summer Olympics, in Los Angeles, using the phrase: Call to the games of the Xth Olympiad Note, that the official numbering of the Winter Olympics does
The majority of Egyptologists agree on the outline and many details of the chronology of Ancient Egypt. This scholarly consensus is the so-called Conventional Egyptian chronology, which places the beginning of the Old Kingdom in the 27th century BC, the beginning of the Middle Kingdom in the 21st century BC and the beginning of the New Kingdom in the mid-16th century BC. Despite this consensus, disagreements remain within the scholarly community, resulting in variant chronologies diverging by about 300 years for the Early Dynastic Period, up to 30 years in the New Kingdom, a few years in the Late Period. In addition, there are a number of "alternative chronologies" outside scholarly consensus, such as the "New Chronology" proposed in the 1990s, which lowers New Kingdom dates by as much as 350 years, or the "Glasgow Chronology", which lowers New Kingdom dates by as much as 500 years. Scholarly consensus on the general outline of the conventional chronology current in Egyptology has not fluctuated much over the last 100 years.
For the Old Kingdom, consensus fluctuates by as much as a few centuries, but for the Middle and New Kingdoms, it has been stable to within a few decades. This is illustrated by comparing the chronology as given by two Egyptologists, the first writing in 1906, the second in 2000; the disparities between the two sets of dates result from additional discoveries and refined understanding of the still incomplete source evidence. For example, Breasted adds a ruler in the Twentieth dynasty that further research showed did not exist. Following Manetho, Breasted believed all the dynasties were sequential, whereas it is now known that several existed at the same time; these revisions have resulted in a lowering of the conventional chronology by up to 400 years at the beginning of Dynasty I. Forming the backbone of Egyptian chronology are the regnal years as recorded in Ancient Egyptian king lists. Surviving king lists are either comprehensive but have significant gaps in their text, or are textually complete but fail to provide a complete list of rulers for a short period of Egyptian history.
The situation is further complicated by occasional conflicting information on the same regnal period from different versions of the same text. Regnal periods have to be pieced together from inscriptions, which will give a date in the form of the regnal year of the ruling pharaoh, yet this only provides a minimum length of that reign and may or may not include any coregencies with a predecessor or successor. In addition, some Egyptian dynasties overlapped, with different pharaohs ruling in different regions at the same time, rather than serially. Not knowing whether monarchies were simultaneous or sequential results in differing chronological interpretations. Where the total number of regnal years for a given ruler is not known, Egyptologists have identified two indicators to deduce that total number: for the Old Kingdom, the number of cattle censuses. A number of Old Kingdom inscriptions allude to a periodic census of cattle, which experts at first believed took place every second year. However, further research has shown that these censuses were sometimes taken in consecutive years, or after two or more years had passed.
The Sed festival was celebrated on the thirtieth anniversary of a pharaoh's ascension, thus rulers who recorded celebrating one could be assumed to have ruled at least 30 years. However, once again, this may not have been standard practice in all cases. In the early days of Egyptology, the compilation of regnal periods was hampered by a profound biblical bias on the part of Egyptologists; this was most pervasive before the mid 19th century, when Manetho's figures were recognized as conflicting with biblical chronology, based on Old Testament references to Egypt. In the 20th century, such biblical bias has been confined to alternative chronologies outside the scholarly mainstream. A useful way to work around these gaps in knowledge is to find chronological synchronisms, which can lead to a precise date. Over the past decades, a number of these have been found, although they are of varying degrees of usefulness and reliability. Seriation, i.e. archeological sequences. This does not fix a person or event to a specific year, but establishing a sequence of events can provide indirect evidence to provide or support a precise date.
For example, some inscribed stone vessels of the rulers of the first two dynasties were collected and deposited in storage galleries beneath and sealed off when the Step Pyramid of Djoser, a Pharaoh of the Third Dynasty, was built. Another example are blocks from the Old Kingdom bearing the names of several kings, which were reused in the construction of Middle Kingdom pyramid-temples at Lisht in the structures of Amenemhat I; the third pylon at Karnak, built by Amenhotep III contained as "fill" material from the kiosk of Sesostris I, along with various stelae of the Second Intermediate Period and the Eighteenth Dynasty of the New Kingdom. Synchronisms with other chronologies, the most important of these being with the Assyrian and Babylonian chronologies, but synchronisms with the Hittites, ancient Palestine, in the final period with ancient Greece, are used; the earliest such synchronism is in the 18th century
1st century BC
The 1st century BC known as the last century BC, started on the first day of 100 BC and ended on the last day of 1 BC. The AD/BC notation does not use a year zero; this is the 100th century in the Holocene calendar. 1st century AD follows. In the course of the century all the remaining independent lands surrounding the Mediterranean were brought under Roman control, being ruled either directly under governors or through puppet kings appointed by Rome; the Roman state itself was plunged into civil war several times resulting in the marginalization of its 500-year-old republic, the embodiment of total state power in a single man—the emperor. The internal turbulence that plagued Rome at this time can be seen as the death throes of the Roman Republic, as it gave way to the autocratic ambitions of powerful men like Sulla, Julius Caesar, Mark Antony and Octavian. Octavian's ascension to total power as the emperor Augustus is considered to mark the point in history where the Roman Republic ends and the Roman Empire begins.
Some scholars refer to this event as the Roman Revolution. It is believed that the birth of Jesus, the central figure of Christianity took place at the close of this century. In the eastern mainland, the Han Dynasty began to decline and the court of China was in chaos in the latter half of this century. Trapped in a difficult situation, the Xiongnu had to begin emigration to the west or attach themselves to the Han. 97 BC: Ariarathes VIII is forced out of Cappadocia by Mithridates VI of Pontus, dies soon afterwards. 96 BC: Cyrene is left to the people of Rome by its ruler Ptolemy Apion. 96 BC: King Alexander Jannaeus of Judea wins the Siege of Gaza. 95 BC: Tigranes the Great becomes king of Armenia 93 BC: Ariobarzanes I Philoromaios becomes king of Cappadocia with Roman backing. 91 BC: The assassination of Marcus Livius Drusus leads to the Social War in Italy 91 BC: Crown Prince Ju Revolt in China. 89 BC: Mithridates VI of Pontus's invasion of Cappadocia leads to the First Mithridatic War with the Roman Republic.
89 BC: Valagamba of Anuradhapura gains control of all of Sri Lanka 88 BC: 80,000 Roman civilians killed in the Asiatic Vespers in Asia Minor 87 BC: Emperor Wu of Han dies and is succeeded by his eight-year-old son Zhao, with Jin Midi, Shangguang Jie and Huo Guang as regents. 88-87 BC: Sulla's first civil war - Sulla marches on Rome and defeats Gaius Marius 86 BC: Siege of Athens ends with Roman conquest of Athens. 86 BC: The death of the regent of China Jin Midi unleashes the rivalry of his co-regents Shangguang Jie and Huo Guang. 85 BC: Sulla defeats the forces of Mithridates VI in Greece at the Battle of Orchomenus 85 BC: Aretas III of the Nabataeans conquers Damascus. 83 BC: Sulla makes peace with Mithridates VI and marches on Rome. 83-81 BC: Lucius Licinius Murena wages the Second Mithridatic War. 82 BC: Sertorius flees from Sulla to North Africa via Hispania c.83 BC: Tigranes of Armenia takes control of Syria after the implosion of the Seleucid dynasty. 81 BC: End of Sulla's second civil war - Sulla is appointed dictator of the Roman state, brings about major reforms.
80 BC: Sertorius invades Hispania and sets up his own regime, beginning the Sertorian War. 80 BC: Conflict between the regents Shangguang Jie and Huo Guang results in the destruction of the Shangguang clan and Huo Guang becoming the de facto ruler of China. C.80 BC: Maues, King of the Sakas, conquers Gandhara and Taxila. 77 BC: Fu Jiezi assassinated the king of Loulan on behalf of the Han dynasty. C.75 BC: Kanva dynasty replaces the Shunga dynasty in Magadha. 74 BC: Mithridates VI of Pontus disputes Nicomedes IV of Bithynia's bequest of his kingdom to the Roman Republic, beginning the Third Mithridatic War. 74 BC: Emperor Zhao of Han dies and is succeeded by the unsuitable Prince He of Changyi and by Xuan. Huo Guang continues to be de facto ruler of China. 73 BC: A slave rebellion led by the escaped gladiator Spartacus leads to the Third Servile War. 73-72 BC: Lucullus defeats Mithridates at Tenedos and the Rhyndacus and he flees east to Armenia 71 BC: Pompey the Great ends the Sertorian War and the Third Servile War.
71 BC: Wusun and China attack the Xiongnu. 69 BC: Lucullus invades Armenia and reestablishes the Seleucids in Syria. 68 BC: Pompey replaces Lucullus as leader of the Roman forces in the Third Mithridatic War. 68 BC: Huo Guang dies and Emperor Xuan of Han assumes full power. The Huo clan is eliminated over the following two years. 67 BC: Pompey is given a three-year extraordinary command against the pirates plaguing the Mediterranean and defeats them in forty days. 66 BC: Pompey drives Mithridates VI out of Asia Minor. 66 BC: Aristobulus II seizes power from John Hyrcanus II in Judea. 63 BC: Mithridates VI commits suicide, ending the Third Mithridatic War. 63 BC: Cicero denounces and defeats the Catilinarian Conspiracy. 63 BC: Pompey captures Jerusalem, establishes Roman annexation of Judea as a client kingdom. He permanently abolishes Seleucid Syria. Aristobulus II of Judea removed from John Hyrcanus II restored as Roman vassal. 62 BC: Nabataean kingdom becomes a Roman vassal. 61 BC: Orgetorix and the Helvetii's attempt to migrate into southwestern France leads Julius Caesar to take military action, beginning the Gallic Wars 60 BC: Julius Caesar, Pompey the Great, Marcus Crassus form the First Triumvirate c. 60 BC: The Sakas conquer Mathura.
58 BC: Battle of Bibracte - Julius Caesar conquers the Helvetii 58 BC: Germans invade Gaul and are defeated by Julius Caesar at Battle of Vosges. 58 BC
The Nanakshahi calendar is a tropical solar calendar, used in Sikhism and is based on the'Barah Maha'. Barah Maha was composed by the Sikh Gurus and translates as the "Twelve Months", it is a poem reflecting the changes in nature which are conveyed in the twelve-month cycle of the Year. The year begins with 1 Chet corresponding to 14 March; the first year of the Nanakshahi Calendar starts in 1469 CE: the year of the birth of Guru Nanak Dev. The Nanakshahi Calendar is named after the founder of Guru Nanak Dev. Sikhs have traditionally recognised luni-solar calendars: the Nanakshahi and Khalsa. Traditionally, both these calendars followed the Bikrami calendar with the Nanakshahi year beginning on Katak Pooranmashi and the Khalsa year commencing with Vaisakhi; the methods for calculating the beginning of the Khalsa era were based on the Bikrami calendar. The year length was the same as the Bikrami solar year. According to Steel, the calendar has twelve lunar months that are determined by the lunar phase, but thirteen months in leap years which occur every 2–3 years in the Bikrami calendar to sync the lunar calendar with its solar counterpart.
Kay abbreviates the Khalsa Era as KE. References to the Nanakshahi Era have been made in historic documents. Banda Singh Bahadur adopted the Nanakshahi calendar in 1710 C. E. after his victory in Sirhind according to which the year 1710 C. E. became Nanakshahi 241. However, Singh states the date of the victory as 14 May 1710 CE. According to Dilagira, Banda "continued adopting the months and the days of the months according to the Bikrami calendar". Banda Singh Bahadur minted new coins called Nanakshahi. Herrli states. Although Banda may have proclaimed this era, it cannot be traced in contemporary documents and does not seem to have been used for dating". According to The Panjab Past and Present, it is Gian Singh who "is the first to use Nanak Shahi Samvats along with those of Bikrami Samvats" in the Twarikh Guru Khalsa. According to Singha, Gian Singh was a Punjabi author born in 1822. Gian Singh wrote the Twarikh Guru Khalsa in 1891; the revised Nanakshahi calendar was designed by Pal Singh Purewal to replace the Bikrami calendar.
The epoch of this calendar is the birth of the first Sikh Guru, Nanak Dev in 1469 and the Nanakshahi year commences on 1 Chet. New Year's Day falls annually on; the start of each month is fixed. According to Kapel, the solar accuracy of the Nanakshahi calendar is linked to the Gregorian civil calendar; this is because the Nanaskhahi calendar uses the tropical year instead of using the sidereal year, used in the Bikrami calendar or the old Nanakshahi and Khalsa calendars. The amended Nanakshahi calendar was adopted in 1998 but implemented in 2003 by the Shiromani Gurdwara Prabhandak Committee to determine the dates for important Sikh events; the calendar was implemented during the SGPC presidency of Sikh scholar Prof. Kirpal Singh Badungar at Takhat Sri Damdama Sahib in the presence of Sikh leadership. Nanakshahi Calendar recognizes the adoption event, of 1999 CE, in the Sikh history when SGPC released the first calendar with permanently fixed dates in the Tropical Calendar. Therefore, the calculations of this calendar do not regress back from 1999 CE into the Bikrami era, fixes for all time in the future.
Features of the Original Nanakshahi calendar: Uses the accurate Tropical year rather than the Sidereal year Called Nanakshahi after Guru Nanak Year 1 is the Year of Guru Nanak's Birth. As an example, April 14, 2019 CE is Nanakshahi 551. Is Based on Gurbani – Month Names are taken from Guru Granth Sahib Contains 5 Months of 31 days followed by 7 Months of 30 days Leap year every 4 Years in which the last month has an extra day Approved by Akal Takht in 2003 In 2010, the Shiromani Gurdwara Prabhandak Committee modified the calendar so that the dates for the start of the months are movable so that they coincide with the Bikrami calendar and changed the dates for various Sikh festivals so they are based upon the lunar phase; this has created controversy with some bodies adopting the original 2003 version called the "Mool Nanakshahi Calendar" and others, the 2010 version. By 2014, the SGPC had scrapped the original Nanakshahi calendar from 2003 and reverted to the Bikrami calendar however it was still published under the name of Nanakshahi.
The Sikh bodies termed it a step taken under pressure from the Shiromani Akali Dal. There is some controversy about the acceptance of the calendar altogether among certain sectors of the Sikh world. SGPC president, Gobind Singh Longowal, on 13 March 2018 urged all Sikhs to follow the current Nanakshahi calendar; the previous SGPC President before Longowal, Prof. Kirpal Singh Badungar, tried to appeal the Akal Takht to celebrate the birthday of Guru Gobind Singh on 23 Poh as per the original Nanakshahi calendar, but the appeal was denied; the PSGPC and a majority of the other gurdwara managements across the world are opposing the modified version of the calendar citing that the SGPC reverted to the Bikrami calendar. They argue that in the Bikrami calendar, dates of many gurpurbs coincide, thereby creating confusion among the Sikh Panth. According to Ahaluwalia, the Nanakshahi calendar goes against the use of lunar Bikrami dates by the Gurus themselves and is contradictory, it begins with the year of birth of
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
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