The Byzantine calendar called "Creation Era of Constantinople" or "Era of the World", was the calendar used by the Eastern Orthodox Church from c. 691 to 1728 in the Ecumenical Patriarchate. It was the official calendar of the Byzantine Empire from 988 to 1453, of Kievan Rus' and Russia from c. 988 to 1700. Since "Byzantine" is a historiographical term, the original name uses the noun "Roman" as it was how the Eastern Roman Empire continued calling itself; the calendar was based on the Julian calendar, except that the year started on 1 September and the year number used an Anno Mundi epoch derived from the Septuagint version of the Bible. It placed the date of creation at 5509 years before the Incarnation, was characterized by a certain tendency, a tradition among Jews and early Christians to number the years from the calculated foundation of the world, its Year One, marking the supposed date of creation, was September 1, 5509 BC, to August 31, 5508 BC. It is not known when; the first appearance of the term is in the treatise of a certain "monk and priest", who mentions all the main variants of the "World Era" in his work.
Georgios argues that the main advantage of the World era is the common starting point of the astronomical lunar and solar cycles, of the cycle of indictions, the usual dating system in Byzantium since the 6th century. He already regards it as the most convenient for the Easter computus. Complex calculations of the 19-year lunar and 28-year solar cycles within this world era allowed scholars to discover the cosmic significance of certain historical dates, such as the birth or the crucifixion of Jesus; this date underwent minor revisions before being finalized in the mid-7th century, although its precursors were developed c. AD 412. By the second half of the 7th century, the Creation Era was known in Western Europe, at least in Great Britain. By the late 10th century around AD 988, when the era appears in use on official government records, a unified system was recognized across the Eastern Roman world; the era was calculated as starting on September 1, Jesus was thought to have been born in the year 5509 since the creation of the world.
Historical time was thus calculated from the creation, not from Christ's birth, as in the west after the Anno Domini system was adopted between 6th and 9th centuries. The Eastern Church avoided the use of the Anno Domini system of Dionysius Exiguus, since the date of Christ's birth was debated in Constantinople as late as the 14th century. Otherwise the Byzantine calendar was identical to the Julian Calendar except that: the names of the months were transcribed from Latin into Greek; the leap day of the Byzantine calendar was obtained in an identical manner to the bissextile day of the original Roman version of the Julian calendar, by doubling the sixth day before the calends of March, i.e. by doubling 24 February. The Byzantine World Era was replaced in the Orthodox Church by the Christian Era, utilized by Patriarch Theophanes I Karykes in 1597, afterwards by Patriarch Cyril Lucaris in 1626, formally established by the Church in 1728. Meanwhile, as Russia received Orthodox Christianity from Byzantium, she inherited the Orthodox Calendar based on the Byzantine Era.
After the collapse of the Byzantine Empire in 1453, the era continued to be used by Russia, which witnessed millennialist movements in Moscow in AD 1492. It was only in AD 1700 that the Byzantine World Era in Russia was changed to the Julian Calendar by Peter the Great, it still forms the basis of traditional Orthodox calendars up to today. September AD 2000 began the year 7509 AM; the earliest extant Christian writings on the age of the world according to the Biblical chronology are by Theophilus, the sixth bishop of Antioch from the Apostles, in his apologetic work To Autolycus, by Julius Africanus in his Five Books of Chronology. Both of these early Christian writers, following the Septuagint version of the Old Testament, determined the age of the world to have been about 5,530 years at the birth of Christ. Ben Zion Wacholder points out that the writings of the Church Fathers on this subject are of vital significance, in that through the Christian chronographers a window to the earlier Hellenistic biblical chronographers is preserved: An immense intellectual effort was expended during the Hellenistic period by both Jews and pagans to date creation, the flood, building of the Temple...
In the course of their studies, men such as Tatian of Antioch, Clement of Alexandria, Hippolytus of Rome
Indian national calendar
The Indian national calendar, sometimes called the Shalivahana Shaka calendar. It is used, alongside the Gregorian calendar, by The Gazette of India, in news broadcasts by All India Radio and in calendars and communications issued by the Government of India; the Saka calendar is used in Java and Bali among Indonesian Hindus. Nyepi, the "Day of Silence", is a celebration of the Saka new year in Bali. Nepal's Nepal Sambat evolved from the Saka calendar. Prior to colonization, the Philippines used to apply the Saka calendar as well as suggested by the Laguna Copperplate Inscription; the term may ambiguously refer to the Hindu calendar. The historic Shalivahana era calendar is still used, it has years. The calendar months follow the signs of the tropical zodiac rather than the sidereal zodiac used with the Hindu calendar. Chaitra has 30 days and starts on March 22, except in leap years, when it has 31 days and starts on March 21; the months in the first half of the year all have 31 days, to take into account the slower movement of the sun across the ecliptic at this time.
The names of the months are derived from older, Hindu lunisolar calendars, so variations in spelling exist, there is a possible source of confusion as to what calendar a date belongs to. Years are counted in the Saka era. To determine leap years, add 78 to the Saka year – if the result is a leap year in the Gregorian calendar the Saka year is a leap year as well, its structure is just like the Persian calendar. Senior Indian Astrophysicist Meghnad Saha was the head of the Calendar Reform Committee under the aegis of the Council of Scientific and Industrial Research. Other members of the Committee were: A. C. Banerjee, K. K. Daftari, J. S. Karandikar, Gorakh Prasad, R. V. Vaidya and N. C. Lahiri, it was Saha's effort. The task before the Committee was to prepare an accurate calendar based on scientific study, which could be adopted uniformly throughout India, it was a mammoth task. The Committee had to undertake a detailed study of different calendars prevalent in different parts of the country. There were thirty different calendars.
The task was further complicated by the fact that religion and local sentiments were integral to those calendars. India's first prime minister, Jawaharlal Nehru, in his preface to the Report of the Committee, published in 1955, wrote: “They represent past political divisions in the country.... Now that we have attained Independence, it is desirable that there should be a certain uniformity in the calendar for our civic and other purposes, this should be done on a scientific approach to this problem.” Usage started at 1 Chaitra 1879, Saka Era, or 22 March 1957. Report of the Calendar Reform Committee – online link. Mapping Time: The Calendar and its History by E. G. Richards, 1998, pp. 184–185. Calendars and their History Indian Calendars Positional astronomy in India Indian National Calendar abstract
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
Kangen was a Japanese era name after Ninji and before Hoji. This period spanned the years from February 1243 to February 1247; the reigning emperor was Go-Saga-tennō. Kangen gannen; the previous era ended and a new one commenced in Ninji 4. 1244: In the spring of this year, a number of extraordinary phenomena in the skies over Kamakura troubled Yoritsune deeply. 1244: Yoritsune's son, had his coming-of-age ceremonies at age 6. In the same month, Yoritsune asked Emperor Go-Saga for permission to give up his responsibilities as shōgun in favor of his son, Kujō Yoritsugu. September 11, 1245: Yoshitsune shaved his head and became a Buddhist priest. 1246: Yoritsune's son, now Shōgun Yoritsugu marries the sister of Hōjō Tsunetoki. 1246: In the 4th year of Go-Saga-tennō's reign, he abdicated. Shortly thereafter, Emperor Go-Fukakusa is said to have acceded to the throne. 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 978-0-231-04940-5.
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
As a means of recording the passage of time, the 14th century was a century lasting from January 1, 1301, to December 31, 1400. During this period and natural disasters ravaged both Europe and the four khanates of the Mongol Empire; the Mongol court was driven out of China and retreated to Mongolia, the Ilkhanate collapsed in Persia, the Chaghatayid dissolved and broke into two parts, the Golden Horde lost its position as a great power in Eastern Europe. In Europe, the Black Death claimed between 75 and 200 million lives – wiping out over 60 percent of European society – while England and France fought in the protracted Hundred Years' War after the death of Charles IV, King of France led to a claim to the French throne by Edward III, King of England; this period is considered the height of chivalry and marks the beginning of strong separate identities for both England and France. The transition from the Medieval Warm Period to the Little Ice Age. Beginning of the Ottoman Empire, early expansion into the Balkans.
Early 14th century: Attributed to Kao Ninga Monk Sewing is made. Kamakura period, it is now kept at The Cleveland Museum of Art. An account of Buddha's life, translated earlier into Greek by Saint John of Damascus and circulated to Christians as the story of Barlaam and Josaphat, became so popular that the two were venerated as saints. Singapore emerges for the first time as a fortified trading centre of some importance. Islam reaches Terengganu, on the Malay Peninsula; the Hausa found several city-states in the south of modern Niger. The poet Petrarch coins the term Dark Ages to describe the preceding 900 years in Europe, beginning with the fall of the Western Roman Empire in 476 through to the renewal embodied in the Renaissance. Iwan vault, Jamé Mosque of Isfahan, Persia, is built. Work begins on the Great Enclosure at Great Zimbabwe, built of dressed stone; the city's population is now between 10,000 and 40,000. 1309 — King Jayanegara succeeds Kertarajasa Jayawardhana as ruler of Majapahit. 1309-1377 — The Avignon papacy transfers the seat of the Popes from Italy to France The Great Famine of 1315-1317 kills millions of people in Europe.
1318-1330 — An Italian Franciscan friar, Mattiussi visited Sumatra and Banjarmasin in Borneo. In his record he described the kingdom of Majapahit. 1320 — Władysław I the Elbow-high is crowned King of Poland which leads to its unification 1323 — Malietoafaiga ordered cannibalism to be abolished in Tutuila, now known as American Samoa. 1325 — Forced out of previous locations, the Mexica found the city of Tenochtitlan 1328 — Tribhuwana Wijayatunggadewi succeeds Jayanegara as ruler of Majapahit. Beginning of the Renaissance in Italy 1335 — The death of the Ilkhan Abu Said, causes the disintegration of the Mongol rule in Persia. 1336 — The Vijayanagara Empire is founded in South India by Harihara 1337 — The Hundred Years' War begins when Edward III of England lays claim to the French throne. 1345–1346 — The French recruit troops and ships in Genoa and Nice. 1346 — English forces led by Edward III defeat a French army led by Philip VI in The Battle of Crécy, a major point in the Hundred Years' War which marks the rise of the longbow as a dominant weapon in Western Europe.
1347–1351 — The Black Death kills around a third of the population of Europe. 1347 — Adityawarman moved the capital of Dharmasraya and established the kingdom of Malayupura in Pagarruyung, West Sumatra. 1350 — Hayam Wuruk, styled Sri Rajasanagara, succeeds Tribhuwana Wijayatunggadewi as ruler of Majapahit. Under its military commander Gajah Mada, Majapahit stretches over much of modern-day Indonesia. 1356 — The Imperial Diet of the Holy Roman Empire headed by Emperor Charles IV issues the Golden Bull of 1356, establishing various constitutional aspects of the Empire, the most significant being the electoral college to elect future emperors. 1356 — The Diet of the Hansa is held in Lübeck, formalising what up until had only been a loose alliance of trading cities in northern Europe and founding the Hanseatic League. 1357 — Scotland retains its independence with the signing of the Treaty of Berwick, thus ending the Wars of Scottish Independence. 1357 — In the Battle of Bubat, the Sundanese royal family is massacred by the Majapahit army by the order of Gajah Mada.
1363 — The Battle of Lake Poyang, a naval conflict between Chinese rebel groups led by Chen Youliang and Zhu Yuanzhang, takes place from August to October, constituting one of the largest naval battles in history. 1365 — The Old Javanese text Nagarakertagama is written. 1366 — Tepanec Tlatoani Acolnahuácatl accepts Acamapichtli as the first tlatoani of Tenochtitlan for the Mexica Empire. 1368 — The end of the Mongol Yuan Dynasty in China and the beginning of the Ming Dynasty. 1377 — Majapahit sends a punitive expedition against Palembang in Sumatra. Palembang's prince, Parameswara flees finding his way to Malacca and establishing it as a major international port. 1378 — The Great Schism of the West begins leading to 3 simultaneous popes. 1378-1382 — Ciompi Revolt occurs in Florence 1381 — John Wycliffe is dismissed from the University of Oxford for criticism of the Roman Catholic Church thus, the Lollardy movement rises in England. 1381 — Peasants' Revolt in England. 1385 — Battle of Aljubarrota between Portugal and Castile.
Portugal maintains independence. 1385 — Union of Krewo between Poland and Lithuania. 1389 — Battle of Kosovo between Serbs and Ottoman Turks, Prince Lazar, sultan Murat I and Miloš Obilić were killed. 1389 — Wikramawardhana succeeds Sri Rajasanagara as ruler of Majapahit. 1392 — Taejo
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