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
Gentoku was a Japanese era name after Karyaku and before Genkō. This period spanned the years from August 1329 through April 1331 in the Southern Court, but continued to be used in the Northern Court until 1332; the reigning Emperor was Go-Daigo-tennō. 1329 Gentoku gannen: The new era name was created to mark an event or series of events. The previous era ended and the new one commenced in Karyaku 4. March 27, 1330: The Emperor visited Tōdai-ji and Kōfuku-ji in Nara. Nussbaum, Louis-Frédéric and Käthe Roth.. Japan encyclopedia. Cambridge: Harvard University Press. ISBN 978-0-674-01753-5. Nihon Odai Ichiran. Paris: Royal Asiatic Society, Oriental Translation Fund of Great Britain and Ireland. OCLC 5850691 Varley, H. Paul.. A Chronicle of Gods and Sovereigns: Jinnō Shōtōki of Kitabatake Chikafusa. New York: Columbia University Press. ISBN 9780231049405.
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 Ethiopian calendar or Eritrean calendar is the principal calendar used in Ethiopia and serves as the liturgical year for Christians in Eritrea and Ethiopia belonging to the Eritrean Orthodox Tewahedo Church, Ethiopian Orthodox Tewahedo Church, Eastern Catholic Churches, the Coptic Orthodox Church of Alexandria, Ethiopian-Eritrean Evangelicalism. It is a solar calendar which in turn derives from the Egyptian calendar, but like the Julian calendar, it adds a leap day every four years without exception, begins the year on August 29 or August 30 in the Julian calendar. A gap of 7–8 years between the Ethiopian and Gregorian calendars results from an alternative calculation in determining the date of the Annunciation. Like the Coptic calendar, the Ethiopic calendar has 12 months of 30 days plus 5 or 6 epagomenal days, which comprise a thirteenth month; the Ethiopian months begin on the same days as those of the Coptic calendar, but their names are in Ge'ez. A 6th epagomenal day is added every 4 years, without exception, on August 29 of the Julian calendar, 6 months before the corresponding Julian leap day.
Thus the first day of the Ethiopian year, 1 Mäskäräm, for years between 1900 and 2099, is September 11. However, it falls on September 12 in years before the Gregorian leap year. Enkutatash is the word for the Ethiopian New Year in Amharic, the official language of Ethiopia, while it is called Ri'se Awde Amet in Ge'ez, the term preferred by the Ethiopian & Eritrean Orthodox Tewahedo Churchs, it occurs on September 11th in the Gregorian Calendar. The Ethiopian Calendar Year 1998 Amätä Məhrät began on the Gregorian Calendar Year on September 11th, 2005. However, the Ethiopian Years 1992 and 1996 began on the Gregorian Dates of'September 12th 1999' and'2003' respectively; this date correspondence applies for the Gregorian years 1900 to 2099. The Ethiopian leap year is every four without exception, while Gregorian centurial years are only leap years when divisible by 400; as the Gregorian year 2000 is a leap year, the current correspondence lasts two centuries instead. The start of the Ethiopian year falls on August 30th.
This date corresponds to the Old-Style Julian Calendar. This deviation between the Julian and the Gregorian Calendar will increase with the passing of the time. You can observe the real start date in the future centuries in a Gregorian to Ethiopian Date Converter. To indicate the year and followers of the Eritrean churches today use the Incarnation Era, which dates from the Annunciation or Incarnation of Jesus on March 25, AD 9, as calculated by Annianus of Alexandria c. 400. Meanwhile, Europeans adopted the calculations made by Dionysius Exiguus in AD 525 instead, which placed the Annunciation 8 years earlier than had Annianus; this causes the Ethiopian year number to be 8 years less than the Gregorian year number from January 1 until September 10 or 11 7 years less for the remainder of the Gregorian year. In the past, a number of other eras for numbering years were widely used in Ethiopia and the Kingdom of Aksum; the most important era – once used by the Eastern Christianity, still used by the Coptic Orthodox Church of Alexandria – was the Era of Martyrs known as the Diocletian Era, or the era of Diocletian and the Martyrs, whose first year began on August 29, 284.
Respective to the Gregorian and Julian New Year's Days, 31⁄2 to 4 months the difference between the Era of Martyrs and the Anni Domini is 285 years. This is because in AD 525, Dionysius Exiguus decided to add 15 Metonic cycles to the existing 13 Metonic cycles of the Diocletian Era to obtain an entire 532 year medieval Easter cycle, whose first cycle ended with the year Era of Martyrs 247 equal to year DXXXI, it is because 532 is the product of the Metonic cycle of 19 years and the solar cycle of 28 years. Around AD 400, an Alexandrine monk called Panodoros fixed the Alexandrian Era, the date of creation, on 29 August 5493 BC. After the 6th century AD, the era was used by Ethiopian chronologists; the twelfth 532 year-cycle of this era began on 29 August AD 360, so 4×19 years after the Era of Martyrs. Bishop Anianos preferred the Annunciation style as 25 March, thus he shifted the Panodoros era by about six months, to begin on 25 March 5492 BC. In the Ethiopian calendar this was equivalent to 15 Magabit 5501 B.
C.. The Anno Mundi era remained in usage until the late 19th century; the 4 year leap-year cycle is associated with the four Evangelists: the first year after an Ethiopian leap year is named the John-year, followed by the Matthew-year, the Mark-year. The year with the 6th epagomenal day is traditionally designated as the Luke-year. There are no exceptions to the 4 year leap-year cycle, like the Julian calendar but unlike the Gregorian calendar; these dates are valid only from March 1900 to February 2100. This is because 1900 and 2100 are not leap years in the Gregorian calendar, while they are still leap year
The Javanese calendar is the calendar of the Javanese people. It is used concurrently with the Gregorian calendar and the Islamic calendar; the Gregorian calendar is the official calendar of the Republic of Indonesia and civil society, while the Islamic calendar is used by Muslims and the Indonesian government for religious worship and deciding relevant Islamic holidays. The Javanese calendar is used by the main ethnicities of Java island—that is, the Javanese and Sundanese people—primarily as a cultural icon and identifier, as a maintained tradition of antiquity; the Javanese calendar is used for cultural and spiritual purposes. The current system of the Javanese calendar was inaugurated by Sultan Agung of Mataram in the Gregorian year 1633 CE. Prior to this, the Javanese had used the Hindu calendar, which begins in 78 CE and uses the solar cycle for calculating time. Sultan Agung's calendar retained the Saka calendar year system of counting, but differs by using the same lunar year measurement system as the Islamic calendar, rather than the solar year.
The Javanese calendar is referred to by its Latin name Anno Javanico or AJ. The Javanese calendar contains multiple, overlapping measurements of times, called "cycles"; these include: the native five-day week, called Pasaran the common Gregorian and Islamic seven-day week the Solar month, called Mangsa the Lunar month, called Wulan the lunar year, or Tahun the octo-ennia cycles, or Windu the 120-year cycle of 15 Windu, called Kurup Days in the Javanese calendar, like the Islamic calendar, begin at sunset. Traditionally, Javanese people do not divide the night into hours, but rather into phases; the division of a day and night are: The native Javanese system groups days into a five-day week called Pasaran, unlike most calendars that uses a seven-day week. The name, pasaran, is derived from the root word pasar, but still today, Javanese villagers gather communally at local markets to meet, engage in commerce, buy and sell farm produce, cooked foods, home industry crafted items and so on. John Crawfurd suggested that the length of the weekly cycle is related to the number of fingers on the hand, that itinerant merchants would rotate their visits to different villages according to a five-day "roster".
The days of the cycle each have two names, as the Javanese language has distinct vocabulary associated with two different registers of politeness: ngoko and krama. The krama names for the days, second in the list, are much less common. ꦊꦒꦶ – ꦩꦤꦶꦱ꧀ ꦥꦲꦶꦁ – ꦥꦲꦶꦠ꧀ ꦥꦺꦴꦤ꧀ – ꦥꦼꦠꦏ꧀ ꦮꦒꦺ – ꦕꦼꦩꦺꦁ ꦏ꧀ꦭꦶꦮꦺꦴꦤ꧀ – ꦲꦱꦶꦃ The origin of the names is unclear, their etymology remains obscure. The names may be derived from indigenous gods, like the European and Asian names for days of the week. An ancient Javanese manuscript illustrates the week with five human figures: a man seizing a suppliant by the hair, a woman holding a horn to receive an offering, a man pointing a drawn sword at another, a woman holding agricultural produce, a man holding a spear leading a bull. Additionally, Javanese consider these days' names to have a mystical relation to colors and cardinal direction: Legi: white and East Pahing: red and South Pon: yellow and West Wage: black and North Kliwon: blurred colors/focus and'center'. Most Markets no longer operate under this traditional Pasaran cycle, instead pragmatically remaining open every day of the Gregorian week.
However many markets in Java still retain traditional names that indicated that once the markets only operated on certain Pasaran days, such as Pasar Legi, or Pasar Kliwon. Some markets in small or medium size locations will be much busier on the Pasaran day than on the other days. On the market's name day itinerate sellers appear selling such things as livestock and other products that are either less purchased or are more expensive; this allows a smaller number of these merchants to service a much larger area much as in bygone days. Javanese astrological belief dictates that an individual’s characteristics and destiny are attributable to the combination of the Pasaran day and the "common" weekday of the Islamic calendar on that person's birthday. Javanese people find great interest in the astrological interpretations of this combination, called the Wetonan cycle; the seven-day-long week cycle is derived from the Islamic calendar, adopted following the spread of Islam throughout the Indonesian archipelago.
The names of the days of the week in Javanese are derived from their Arabic counterparts, namely: These two-week systems occur concurrently. This combination forms the Wetonan cycle; the Wetonan cycle superimposes the five-day Pasaran cycle with the seven-day week cycle. Each Wetonan cycle lasts for 35 days. An example of Wetonan cycle: From the example above, the Weton for Tuesday May 6, 2008 would be read as Selasa Wage; the Wetonan cycle is important for divinatory systems, important celebrations, rites of passage. Commemorations and events are held on days considered to be auspicious. An prominent example, still taught in primary schools, is that the Weton for the Proclamation of Indonesian Independence on 17 August 1945 took place on Jumat Legi. Therefore, Jumat Legi is considered an important night for pilgrimage. There are taboos
As a means of recording the passage of time, the 13th century was the century which lasted from January 1, 1201 through December 31, 1300 in accordance with the Julian calendar in the Common Era. In the history of European culture, this period is considered part of the High Middle Ages, after its conquests in Asia the Mongol Empire stretched from Eastern Asia to Eastern Europe. 1202 – Introduction of Liber Abaci by Fibonacci. 1202 – Battle of Basian occurred on July 27, between Kingdom of Georgia and Seljuks. 1204 – Fourth Crusade of 1202–1204 captures Zara for Venice and sacks Byzantine Constantinople, creating the Latin Empire. 1204 – Fall of Normandy from Angevin hands to the French King, Philip Augustus, end of Norman domination of France. 1205 – The Battle of Adrianople occurred on April 14 between Bulgarians under Tsar Kaloyan of Bulgaria, Crusaders under Baldwin I, the first emperor of the Latin Empire of Constantinople. 1206 – Genghis Khan is declared Great Khan of the Mongols.? – The Marinids settled Zughba Arab from the Chelif Valley to Tamesna or they cohabit with the Zenata Berber.
1212 – The Battle of Las Navas de Tolosa in Iberia marks the beginning of a rapid Christian reconquest of the southern half of the Iberian peninsula from 1230–1248, with the defeat of Moorish forces. 1213 – France defeats the Spanish Kingdom of Aragon at the Battle of Muret. 1214 – France defeats English and Imperial German forces at the Battle of Bouvines. 1215 – King John signs Magna Carta at Runnymede. 1217–1221 – Fifth Crusade captures Egyptian Ayyubid port city of Damietta. 1221 – Venice signs a trade treaty with the Mongol Empire. 1222 – Andrew II of Hungary signs the Golden Bull which affirms the privileges of Hungarian nobility. 1223 – The Signoria, of the Republic of Venice is formed and consists of the Doge, the Minor Council, the three leaders of the Quarantia. 1223 – The Mongol Empire defeats various Russian principalities at the Battle of the Kalka River. 1223 – Volga Bulgaria defeats the army of the Mongol Empire at the Battle of Samara Bend 1227 – Estonians are subjugated to German crusader rule during the Livonian Crusade.
1228–1229 – Sixth Crusade under the excommunicated Frederick II Hohenstaufen, who returns Jerusalem to the Crusader States. 1228–1230 – First clash between Gregory IX and Frederick II. 1226–1250 – Dispute between the so-called second Lombard League and Frederick II. 1232 – The Mongols besiege Kaifeng, the capital of the Jin dynasty, capturing it in the following year. 1233 – Battle of Ganter, Ken Arok defeated Kertajaya, the last king of Kediri, thus established Singhasari kingdom Ken Arok ended the reign of Isyana Dynasty and started his own Rajasa dynasty. 1235 – The Mandinka tribes unite to form the Mali Empire which leads to the downfall of Takrur in the 1280s. 1239–1250 – Third conflict between Holy Roman Empire and Papacy. 1237–1240 – Mongol Empire conquers Kievan Rus. 1238 – Sukhothai was the first capital of Sukhothai Kingdom. 1241 – Mongol Empire defeats Hungary at the Battle of Mohi and defeats Poland at the Battle of Legnica. Hungary and Poland ravaged. 1242 – Russians defeat the Teutonic Knights at the Battle of Lake Peipus.
1243–1250 – Second Holy Roman Empire–Papacy War. 1244 – Ayyubids and Khwarezmians defeat the Crusaders and their Arab allies at the Battle of La Forbie. 1249 – End of the Portuguese Reconquista against the Moors, when King Afonso III of Portugal reconquers the Algarve. 1248–1254 – Seventh Crusade captures Egyptian Ayyubid port city of Damietta, Crusaders withdraw. Mamelukes overthrow Ayyubid Dynasty. 1257 – Baab Mashur Malamo established the Kingdom of Ternate in Maluku. 1258 – Baghdad captured and destroyed by the Mongols, effective conclusion of the Caliphate. 1259 – Treaty of Paris. 1260 – Toluid Civil War begins between Kublai Khan and Ariq Böke for the title of Great Khan. 1261 – Byzantines under Michael VIII retake Constantinople from the Crusaders and Venice. 1262 – Iceland was brought under Norwegian rule, with the Old Covenant. 1265 – Dominican friar and theologian, Thomas Aquinas begins to write his Summa Theologiae. 1268 – Fall of the Crusader State of Antioch to the Mamelukes. 1270 – Goryeo dynasty swears allegiance to the Yuan dynasty.
1271 – Edward I of England and Charles of Anjou arrive in Acre, starting the Ninth Crusade against Baibars. 1272–1274 – Second Council of Lyon attempts to unite the churches of the Eastern Roman Empire with the Church of Rome. 1274 – The Tepanec give the Mexica permission to settle at an islet, named Cauhmixtitlan 1275 – Sant Dnyaneshwar who wrote Dnyaneshwari and Amrutanubhav was born. 1275 – King Kertanegara of Singhasari launched Pamalayu expedition against Melayu Kingdom in Sumatra. 1277 – Passage of the last and most important of the Paris Condemnations by Bishop Tempier, which banned a number of Aristotelian propositions 1279 – The Song dynasty ends after losing the Battle of Yamen to the Mongols. 1282 – Aragon acquires Sicily after the Sicilian Vespers. 1284 – Peterhouse, Cambridge founded by Hugo de Balsham, the bishop of Ely. 1284 – King Kertanegara launched Pabali expedition to Bali, which integrated Bali into the Singhasari territory. 1285 – Second Mongol raid against Hungary, led by Nogai Khan.
1289 – The County of Tripoli falls to the Bahri Mamluks led by Qalawun. 1289 – Kertanegara insulted the envoy of Kublai Khan, who demanded Java to pay tribute to Yuan Dynasty. 1291 – The Swiss Confederation of Uri and Unterwalden forms. 1291 – Mamluk Sultan of Egypt al-Ashraf Khalil captures Acre, thus ending the Crusader Kingdom of Jerusalem. 1292 – Jayakatwang, duke of Kediri and killed Kertanegara, ended the Singhasari kin
Japanese calendar types have included a range of official and unofficial systems. At present, Japan uses the Gregorian calendar together with year designations stating the year of the reign of the current Emperor; the lunisolar Chinese calendar was introduced to Japan via Korea in the middle of the sixth century. After that, Japan calculated its calendar using various Chinese calendar procedures, from 1685, using Japanese variations of the Chinese procedures, but in 1873, as part of Japan's Meiji period modernization, a calendar based on the solar Gregorian calendar was introduced. In Japan today, the old Chinese calendar is ignored. Japan has had more than one system for designating years. Including: The Chinese sexagenary cycle was introduced early into Japan, it was used together with era names, as in the 1729 Ise calendar shown above, for "the 14th year of Kyōhō, tsuchi-no-to no tori", i.e. 己酉. Now, the cycle is used except around New Year; the era name system was introduced from China, has been in continuous use since AD 701.
Since the Taishō Emperor's ascension in 1912, each emperor's reign has begun a new era. Nengō are the official means of dating years in Japan, all government business is conducted using that system, it is in general use in private and personal business. The Japanese imperial year is based on the date of the legendary founding of Japan by Emperor Jimmu in 660 BC, it was first used in the official calendar in 1873. However, it never replaced era names, since World War II has been abandoned; the Western Common Era system has come into common use since the Meiji period. Now, most people know it, as well as era names; the official dating system known as nengō, has been in use since the late 7th century. Years are numbered within eras. Beginning with Meiji, each reign has been one era, but many earlier Emperors decreed a new era upon any major event; the nengō system remains in wide use on official documents and government forms. The imperial year system was used from 1872 to the Second World War. Imperial year 1 was the year when the legendary Emperor Jimmu founded Japan – 660 BC according to the Gregorian Calendar.
Usage of kōki dating can be a nationalist signal, pointing out that the history of Japan's imperial family is longer than that of Christianity, the basis of the Anno Domini system. Kōki 2600 was a special year; the 1940 Summer Olympics and Tokyo Expo were planned as anniversary events, but were canceled due to the Second Sino-Japanese War. The Japanese naval Zero Fighter was named after this year. After the Second World War, the United States occupied Japan, stopped the use of kōki by officials. Today, kōki is used, except in some judicial contexts; the 1898 law determining the placement of leap years is based on the kōki years, using a formula, equivalent to that of the Gregorian calendar: if the kōki year number is evenly divisible by four, it is a leap year, unless the number minus 660 is evenly divisible by 100 and not by 400. Thus, for example, the year Kōki 2560 is divisible by 4; the Japanese government has announced a new period of year on 2019 April Reiwa. The Heisei Period will end on 2019 April 30 and so the new period of year is expected to start on first of May 2019.
See "Seasonal days", below. The modern Japanese names for the months translate to "first month", "second month", so on; the corresponding number is combined with the suffix 月. The table below uses traditional numerals. In addition, every month has a traditional name, still used by some in fields such as poetry; the opening paragraph of a letter or the greeting in a speech might borrow one of these names to convey a sense of the season. Some, such as Yayoi and Satsuki, do double duty as given names; these month names appear from time to time on jidaigeki, contemporary television shows and movies set in the Edo period or earlier. The old Japanese calendar was an adjusted lunar calendar based on the Chinese calendar, the year—and with it the months—started anywhere from about 3 to 7 weeks than the modern year, so in historical contexts it is not accurate to equate the first month with January. Japan uses a seven-day week, aligned with the Western calendar; the seven-day week, with names for the days corresponding to the Latin system, was brought to Japan around AD 800 with the Buddhist calendar.
The system was used for astrological purposes and little else until 1876. The names of the days come from the five visible planets, which in turn are named after the five Chinese elements, from the moon and sun. On the origin of the names of the days of the week see East Asian Seven Luminaries. Sunday and Saturday are regarded as "Western style take-a-rest days". Since the late 19th century, Sunday has been regarded as a "full-time holiday", Saturday a half-time holiday; these holidays have no religious meaning. Many Japanese retailers