Japanese calendar

Japanese calendartypes have included a range of official and unofficial systems. At present, Japan uses theGregorian calendartogether with year designations stating theyear of the reign of the current Emperor.The written form starts with the year, then the month and finally the day, coinciding with theISO 8601standard.
For example, February 16, 2003, can be written as either2003年2月16日or平成15年2月16日(the latter following the regnal year system).年readsnenand means "year",月readsgatsuand means "month", and finally日(usually) readsnichi(its pronunciation depends on the number that precedes it, see below) and means "day".
Prior to the introduction of the Gregorian calendar in 1873, the reference calendar was based on thelunisolarChinese calendar.
Over the centuries, Japan has used up to four systems for designating years:the Chinesesexagenary cycle, theera name(元号,gengō)system, theJapanese imperial year(皇紀(kōki)or紀元(kigen)) and the WesternCommon Era(Anno Domini)(西暦,seireki)system. In the 21st century, however, the era system (gengō) and Western system (seireki) are the only ones still widely used.
ThelunisolarChinese calendarwas introduced to Japan via Korea in the middle of the sixth century. After that, Japan calculated its calendar using various Chinese calendar procedures, and from 1685, using Japanese variations of the Chinese procedures.Itssexagenary cyclewas often used together with era names, as in the 1729 Ise calendar shown above, which is for "the 14th year of Kyōhō, tsuchi-no-to no tori", i.e.,己酉.
In modern times, the old Chinese calendar is virtually ignored; celebrations of theLunar New Yearare thus limited toChineseand other Asian immigrant communities. However, its influence can still be felt in the idea of "lucky and unlucky days" (described below), the traditional meanings behind the name of each month, and other features of modern Japanese calendars.
Theera name(元号,gengō)system was also introduced from China, and has been in continuous use since AD 701.The reigningEmperorchooses the name associated with theirregnal eras; before 1868, multiple names were chosen throughout the same emperor's rule, such as to commemorate a major event.For instance, theEmperor Kōmei's reign (1846–1867) was split into seven eras, one of which lastedonly one year.Starting with Kōmei's son theEmperor Meijiin 1868, there has only been onegengōper emperor representing their entire reign.
Thenengōsystem remains in wide use, especially on official documents and government forms.It is also in general use in private and personal business.
The present era,Reiwa, formally began on 1 May 2019.The name of the new era was announced by theJapanese governmenton 1 April 2019, a month prior toNaruhito's accession to the throne.The previous era,Heisei, came to an end on 30 April 2019, after Japan's former emperor,Akihito, abdicated the throne.Reiwa is the first era name whose characters come from a Japanese root source; prior eras' names were taken from Chinese classic literature.
TheJapanese imperial year(皇紀(kōki)or紀元(kigen)) is based on the date of the legendary founding of Japan byEmperor Jimmuin 660 BC.For instance, 660 BC is counted asKōki1.
It was first used in the official calendar in 1873.Kōki2600 (1940) was a special year. The1940 Summer OlympicsandTokyo Expowere planned as anniversary events, but were canceled due to theSecond Sino-Japanese War. The Japanese navalZero Fighterwas named after this year. After theSecond World War, theUnited States occupied Japan, and stopped the use ofkōkiby officials.
Today,kōkiis rarely used, except in some judicial contexts.Usage ofkōkidating can be anationalistsignal, pointing out that the history of Japan's imperial family is longer than that ofChristianity, the basis of theAnno Domini(AD) system.
The 1898 law determining the placement ofleap yearsis officially based on thekōkiyears, using a formula that is effectively equivalent to that of theGregorian calendar: if thekōkiyear 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 yearKōki2560 (AD 1900) is divisible by 4; but 2560 − 660 = 1900, which is evenly divisible by 100 and not by 400, sokōki2560 (1900) was not a leap year, just as in most of the rest of the world.
The WesternCommon Era(Anno Domini)(西暦,seireki)system, based on thesolarGregorian calendar, was first introduced in 1873 as part of the Japan'sMeiji periodmodernization.
Nowadays, Japanese people know it as well as the regnal eras.
There are four seasons corresponding to the West's:
However, there is also a traditional system of72 microseasons(候,kō), consisting of24 solar terms(節気,sekki)each divided into three sets of five days,and with specially-named days orZassetsu(雑節)indicating the start and end of each. This system was adapted from the Chinese in 1685 by court astronomer Shibukawa Shunkai, rewriting the names to better match the local climate and nature in his native Japan.Eachkōhas traditional customs, festivals, foods, flowers and birds associated with it:
Zassetsu(雑節)is a collective term for special seasonal days within the 24sekki.
Shanichidates can vary by as much as 5 days.Chūgenhas a fixed day. All other days can vary by one day.
Manyzassetsudays occur in multiple seasons:
The termSetsubun(節分)originally referred to the eves ofRisshun(立春, 315°, the beginning of Spring),Rikka(立夏, 45°, the beginning of Summer),Risshū(立秋, 135°, the beginning of Autumn), andRittō(立冬, 225°, the beginning of Winter); however, it now only refers to the day beforeRisshun.
As mentioned above, the Japanese calendar used to be based on an adaptation of the Chinese lunar calendar, which begins 3 to 7 weeks later than the Gregorian. In other words, the Gregorian "first month" and the Chinese "first month" do not align, which is important in historical contexts.
The "traditional names" for each month, shown below, are still used by some in fields such aspoetry; of the twelve,Shiwasuis still widely used today. 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 asYayoiandSatsuki, do double duty asgiven names(for women). These month names also appear from time to time onjidaigeki, contemporary television shows and movies set in theEdo periodor earlier.
The Japanese names for the modernGregorianmonths literally translate to "first month", "second month", and so on. The corresponding number is combined with the suffix月(-gatsu, "month"). The table below uses traditional numerals, but the use ofWestern numerals(１月,２月,３月, etc.) is common.
Japan uses aseven-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 theBuddhist calendar. The system was used for astrological purposes and little else until 1876.
Much like in multiple European languages, in which the names for weekdays are, partially or fully, based on what the Ancient Romans considered the seven visible planets, meaning the five visible planets and the sun and the moon, in The Far East the five visible planets are named after thefive Chinese elements(metal, wood, water, fire, earth.) On the origin of the names of the days of the week, also seeEast 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", and Saturday a half-time holiday(半ドン,han-don). These days have no religious meaning (except those who believe inChristianityorJudaism). Many Japanese retailers do not close on Saturdays or Sundays, because many office workers and their families are expected to visit the shops during the weekend. Sunday is traditionally the first day of the week.
Japanese people also use 10-day periods calledjun(旬). Each month is divided into two 10-day periods and a third with the remaining 8 to 11 days:
These are frequently used to indicate approximate times, for example, "the temperatures are typical of thejōjunof April"; "a vote on a bill is expected during thegejunof this month." The magazineKinema Junpowas originally published once everyjun(i.e. three times a month).
The table below shows dates written with traditional numerals, but use of Arabic numerals (１日,２日,３日, etc.) is extremely common in everyday communication, almost the norm.
Each day of the month has a semi-systematic name. The days generally usekun(native Japanese)numeral readingsup to ten, and thereafteron(Chinese-derived) readings, but there are some irregularities.
Tsuitachiis a worn-down form oftsuki-tachi(月立ち), literally "month start." The last day of the month was calledtsugomori, which means "Moon hidden." This classical word comes from the tradition of the lunisolar calendar.
The 30th was also traditionally calledmisoka, just as the 20th is calledhatsuka. Nowadays, the terms for the numbers 28–31 plusnichiare much more common. However,misokais much used in contracts, etc., specifying that a payment should be made on or by the last day of the month, whatever the number is.New Year's Eveis known asŌmisoka(大晦日, big 30th), and that term is still in use.
As mentioned below, there is traditional belief that some days are lucky (kichijitsu) or unlucky. For example, there are some who will avoid beginning something on an unlucky day.
The first day of April has broad significance in Japan. It marks the beginning of the government's fiscal year.Many corporations follow suit. In addition, corporations often form or merge on that date. In recent years, municipalities have preferred it for mergers. On this date, many new employees begin their jobs, and it is the start of many real-estate leases. Theschool yearbegins on April 1.
Therokuyō(六曜)are a series of six days calculated from the date ofChinese calendarthat supposedly predict whether there will be good or bad fortune during that day.  Therokuyōare commonly found on Japanese calendars and are often used to plan weddings and funerals, though most people ignore them in ordinary life. Therokuyōare also known as therokki(六輝).  In order, they are:
Therokuyōdays are easily calculated from the Japanese lunisolar calendar. The first day of the first month is alwayssenshō, with the days following in the order given above until the end of the month. Thus, the 2nd day istomobiki, the 3rd issenbu, and so on. The 1st day of the 2nd month restarts the sequence attomobiki. The 3rd month restarts atsenbu, and so on for each month. The latter six months repeat the patterns of the first six, so the 1st of the 7th issenshō, the 1st of the 12th isshakkōand themoon-viewing dayon the 15th of the 8th is alwaysbutsumetsu.
This system did not become popular in Japan until the end of the Edo period.
After World War II, the names of Japanese national holidays were completely changed because of the secular state principle (Article 20, The Constitution of Japan). Although many of them actually originated fromShinto,Buddhismand important events relating to the Japanese imperial family, it is not easy to understand the original meanings from the superficial and vague official names.
Notes: Single days between two national holidays are taken as a bank holiday. This applies to May 4, which is a holiday each year. When a national holiday falls on a Sunday the next day that is not a holiday (usually a Monday) is taken as a holiday.
The following are known as the five seasonal festivals(節句,sekku), also known asgosekku(五節句). Thesekkuwere made official holidays duringEdo periodon Chineselunisolar calendar. The dates of these festivals are confused nowadays; some on the Gregorian calendar, others on "Tsuki-okure".
Notsekku:
In contrast to other East Asian countries such asChina,Vietnam,KoreaandMongolia, Japan has almost completely forgotten theChinese calendar. Since 1876, January has been officially regarded as the "first month" even when setting the date of Japanese traditionalfolkloreevents (other months are the same: February as the second month, March as the third, and so on). But this system often brings a strong seasonal sense of gap since the event is 3 to 7 weeks earlier than in the traditional calendar. Modern Japanese culture has invented a kind of "compromised" way of setting dates for festivals calledTsuki-okure("One-Month Delay") orChūreki("The Eclectic Calendar").
The festival is celebrated just one solar calendar month later than the date on the Gregorian calendar. For example, the Buddhist festival ofObonwas the 15th day of the 7th month. In many places the religious services are held on 15 July. However, in some areas, the rites are normally held on 15 August, which is more seasonally close to the old calendar. (The general term "Obon holiday" always refers to the middle of August.) Although this is just de facto and customary, it is broadly used when setting the dates of many folklore events and religious festivals. ButJapanese New Yearis the great exception. The date ofJapanese New Yearis always 1 January.