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TheJapanese era name (Japanese:元号,Hepburn:gengō, "era name") ornengō (年号,year name), is the first of the two elements that identify years in theJapanese era calendar scheme. The second element is a number which indicates the year number within the era (with the first year being "gan (元)", meaning "origin, basis"), followed by the literal "nen (年)" meaning "year".

Era names originated in 140 BCE inImperial China, during the reign of theEmperor Wu of Han.^[1][2] As elsewhere in theSinosphere, the use of era names was originally derived from Chinese imperial practice,^[2][3][4] although the Japanese system is independent of the Chinese,Korean, andVietnamese era name systems. Unlike its other Sinosphere counterparts, Japanese era names are still in official use. Government offices usually require era names and years for official papers.

The five era names used since the end of theEdo period in 1868 can be abbreviated by taking the first letter of theirromanized names. For example, S55 means Shōwa 55 (i.e. 1980), and H22 stands for Heisei 22 (2010). At 62 years and 2 weeks,Shōwa is the longest era to date.

TheReiwa (令和)^[5] era began on 1 May 2019, the day of accession ofNaruhitoto the throne as the 126thEmperor of Japan,^[6] following the day of the planned and voluntaryabdication^[7] of his father, the 125th Emperor,Akihito. Emperor Akihito had receivedspecial permission to abdicate,^[8] rather than serving in his role until his death, as is the rule.^[9] The Reiwa era follows the 31st and final year of theHeisei era (平成31年), which had started on the day after the death of EmperorHirohito on 8 January 1989.

A graphical timeline is available at Japanese era names

The system on which the Japanese era names are based originated in China in 140 BCE, and was adopted by Japan in 645 CE, during the reign ofEmperor Kōtoku.

The first era name to be assigned was "Taika" (大化), celebrating the political and organizational changes which were to flow from the greatTaika reform (大化の改新) of 645. Although the regular practice of proclaiming successive era names was interrupted in the late seventh century, it was permanently re-adopted in 701 during the reign of Emperor Monmu (697–707). Since then, era names have been used continuously up through the present day.^[10]

Prior to theMeiji period, era names were decided by court officials and were subjected to frequent change. A new era name was usually proclaimed within a year or two after the ascension of a new emperor. A new era name was also often designated on the first, fifth and 58th years of thesexagenary cycle, because they were inauspicious years inOnmyōdō. These three years are respectively known askakurei,kakuun, andkakumei, and collectively known assankaku. Era names were also changed due to other felicitous events or natural disasters.

In historical practice, the first day of a nengō (元年,gannen) starts whenever the emperor chooses; and the first year continues until the next lunar new year, which is understood to be the start of the nengō's second year.^[11]

Era names indicate the various reasons for their adoption. For instance, the nengō Wadō (和銅), during the Nara period, was declared due to the discovery of copper deposits inChichibu. Most nengō are composed of twokanji, except for a short time during theNara period when four-kanji names were sometimes adopted to follow the Chinese trend. Tenpyō Kanpō (天平感宝), Tenpyō Shōhō (天平勝宝), Tenpyō Hōji (天平宝字) and Tenpyō Jingo (天平神護) are some famous nengō names that use four characters. Since theHeian period,Confucian thoughts and ideas have been reflected in era names, such as Daidō (大同), Kōnin (弘仁) and Tenchō (天長).^{[citation needed]} Although there currently exist a total of 248 Japanese era names, only 73 kanji have been used in composing them. Out of these 73 kanji, 31 of them have been used only once, while the rest have been used repeatedly in different combinations.

The vast majority of Japanese Era Names were used for less than 10 years, with two being used for less than a year. Only 28 have been used for more than 10 years and less than 30 years. Only Heisei, Ōei, Meiji, and Showa have been used for more than 30 years.

Mutsuhito assumed the throne in 1867, during the third year of theKeiō (慶応) era. On 23 October 1868, the era name was changed to "Meiji" (明治), and a "one reign, one era name" (一世一元,issei-ichigen) system was adopted, wherein era names would change only upon immediate imperial succession. This system is similar to the now-defunct Chinese system used since the days of theMing dynasty, in which the era name was not updated until the year following the emperor's death.

In modern practice, the first year of a nengō (元年,gannen) starts immediately upon the emperor's accession and ends on 31 December. Subsequent years follow theGregorian calendar. For example, the Meiji era lasted until 30 July 1912, when the Emperor died and theTaishō (大正) era was proclaimed. 1912 is therefore known as both "Meiji 45" and "Taishō 1" (大正元年,Taishō gannen), although Meiji technically ended on 30 July with Mutsuhito's death.

This practice, implemented successfully since the days of Meiji but never formalized, became law in 1979 with the passage of the Era Name Law (元号法,gengō-hō). Thus, since 1868, there have only been five era names assigned: Meiji, Taishō, Shōwa, Heisei, and Reiwa, each corresponding with the rule of only one emperor. Upon death, the emperor is thereafter referred to by the era of his reign. For example, Mutsuhito is posthumously known as "Emperor Meiji" (明治天皇,Meiji Tennō).

It is protocol in Japan that the reigning emperor be referred to asTennō Heika (天皇陛下, "His Majesty the Emperor") orKinjō Tennō (今上天皇, "current emperor"). To call the current emperor by the current era name, i.e. "Reiwa", even in English,^{[citation needed]} is a faux pas, as this is – and will be – hisposthumous name. Use of the emperor's given name (i.e., "Naruhito") is rare, and is considered vulgar behaviour in Japanese.

TheEmperor Akihito abdicated on 30 April 2019, necessitating a change in nengō. The new name, made public on the morning of 1 April of the same year, isReiwa (令和).^[5]

The era name system that was introduced byEmperor Kōtoku was abandoned after his death; no era names were designated between 654 and 686. The system was briefly reinstated byEmperor Tenmu in 686, but was again abandoned upon his death about two months later. In 701,Emperor Monmu once again reinstated the era name system, and it has continued uninterrupted through today.

Although use of theGregorian calendar for historical dates became increasingly common in Japan, the traditional Japanese system demands that dates be written in reference to era names. The apparent problem introduced by the lack of era names was resolved by identifying the years of an imperial reign as a period.^[12]

Although in modern Japan posthumous imperial names correspond with the eras of their reign, this is a relatively recent practice, introduced during theMeiji period and instituted by law in 1979. Therefore, the posthumous names of the emperors and empresses who reigned prior to 1868 may not be taken as era names by themselves. For example, the year 572—the year in whichEmperor Bidatsu assumed theChrysanthemum Throne – is properly written as "敏達天皇元年" (Bidatsu-Tennō Gannen, "the first year of Emperor Bidatsu"), and not "敏達元年" (Bidatsu Gannen, "the first year of Bidatsu"), although it may be abbreviated as such.^[13] By incorporating both proper era names and posthumous imperial names in this manner, it is possible to extend the nengō system to cover all dates from 660 BCE through today.^[14]

In addition to the official era name system, in which the era names are selected by the imperial court, one also observes—primarily in the ancient documents and epigraphs of shrines and temples—unofficial era names calledshinengō (私年号, "personal era name"), also known asginengō (偽年号) orinengō (異年号). Currently, there are over 40 confirmed shinengō, most of them dating from themiddle ages.Shinengō used prior to the reestablishment of the era name system in 701 are usually calleditsunengō (逸年号).^[a]

Because official records ofshinengō are lacking, the range of dates to which they apply is often unclear. For example, the well-known itsunengō Hakuhō (白鳳) is normally said to refer to 650–654 CE; a poetic synonym for theHakuchi era. However, alternate interpretations exist. For example, in theNichūreki, Hakuhō refers to 661–683 CE, and in some medieval temple documents, Hakuhō refers to 672–685 CE. Thus, shinengō may be used as an alternative way of dating periods for which there is no official era name.

Other well-knownitsunengō andshinengō include Hōkō (法興) (591–621+ CE), Suzaku (朱雀) (686), Entoku (延徳) (1460), Miroku (弥勒) (1506–1507 or 1507–1509) and Meiroku (命禄) (1540–1543).

The most recentshinengō is Seiro (征露) (1904–1905), named for theRusso-Japanese War.

Edo period scholarTsurumine Shigenobu proposed that Kyūshū nengō (九州年号), said to have been used in ancientKumaso, should also be considered a form ofshinengō. This claim is not generally recognized by the academic community. Lists of the proposedKyūshū nengō can be seen in the Japanese language entries鶴峯戊申 and九州王朝説.

Certain era names have specific characters assigned to them, for instance ㋿ for theReiwa period, which can also be written as令和. These are included inUnicode: Code points U+32FF (㋿), U+337B (㍻), U+337C (㍼), U+337D (㍽) and U+337E (㍾) are used for the Reiwa, Heisei, Shōwa, Taishō and Meiji eras, respectively.

Certain calendar libraries support the conversion from and to the era system, as well as rendering of dates using it.

Since the release ofJava 8, theJapanese calendar is supported in the new Date and time API for the year Meiji 6 (1873) onwards.^[15]

Computers and software manufacturers needed to test their systems in preparation forthe new era which began on 1 May 2019.Windows provided a test mechanism to simulate a new era ahead of time.^[16]Java Development Kit 11 supported this era using the placeholders "元号" for Japanese, "NewEra" for other languages.^[17] The final name was added in JDK 12.0.1, after it was announced by the Japanese government.^[18]

Unicode code point U+32FF (㋿) was reserved for representing the new era name, Reiwa.^{[19][20][21][22][23][24]}

Thelist of Japanese era names is the result of aperiodization system which was established byEmperor Kōtoku in 645. The system of Japanese era names (年号,nengō, "year name") was irregular until the beginning of the 8th century.^[25] After 701, sequential era names developed without interruption across a span of centuries.^[10] As of 1 April 2019, there have been 239 era names.

To convert a Japanese year to aGregorian calendar year, find the first year of the Japanese era name (also callednengō). When found, add the number of the Japanese year, then subtract 1.

The "one reign, one era name" (一世一元) system was implemented in 1868 CE.

Unofficial non-nengōperiods (shinengō) before 701 are calleditsunengō (逸年号). Pre-Taika chronology intervals include:

• Reign of Emperor Jimmu, 660–581 BCE
• Reign of Emperor Suizei, 581–548 BCE
• Reign of Emperor Annei, 548–510 BC
• Reign of Emperor Itoku, 510–475 BCE
• Reign of Emperor Kōshō, 475–392 BCE
• Reign of Emperor Kōan, 392–290 BC
• Reign of Emperor Kōrei, 290–214 BCE
• Reign of Emperor Kōgen, 214–157 BCE
• Reign of Emperor Kaika, 157–97 BCE
• Reign of Emperor Sujin, 97–29 BCE
• Reign of Emperor Suinin, 29 BCE– 71 CE
• Reign of Emperor Keikō, 71–131 CE
• Reign of Emperor Seimu, 131–192
• Reign of Emperor Chūai, 192–201
• Regency of Empress Jingū, 201–270
• Reign of Emperor Ōjin, 270–313
• Reign of Emperor Nintoku, 313–400
• Reign of Emperor Richū, 400–406
• Reign of Emperor Hanzei, 406–412
• Reign of Emperor Ingyō, 412–454
• Reign of Emperor Ankō, 454–457
• Reign of Emperor Yūryaku, 457–480
• Reign of Emperor Seinei, 480–485
• Reign of Emperor Kenzō, 485–488
• Reign of Emperor Ninken, 488–499
• Reign of Emperor Buretsu, 499–507
• Reign of Emperor Keitai, 507–534
• Reign of Emperor Ankan, 534–536
• Reign of Emperor Senka, 536–540
• Reign of Emperor Kinmei, 540–572
• Reign of Emperor Bidatsu, 572–586
• Reign of Emperor Yōmei, 586–588
• Reign of Emperor Sushun, 588–593
• Reign of Emperor Suiko, 593–629^[b]
• Reign of Emperor Jomei, 629–645

Post-Taika chronology intervals not covered by thenengō system include:

• Reign of Empress Saimei, 655–662^[105] ...Saimei (period)^[12]
• Reign of Emperor Tenji, 662–672^[106] ...Tenji (period)^[12]
• Reign of Emperor Kōbun, 672–673^[107] ...Kōbun (period) orSujaku^[12] (or Suzaku)
• Reign of Emperor Tenmu, 673–686^[108] ...Tenmu (period) orHakuhō period^[12][109]
• Reign of Empress Jitō, 687–697^[110] ...Jitō (period)^[12]
• Reign of Emperor Monmu, 697–701^[111] ...Monmu (period)^[12]

• Calendar
• Japanese calendar
• Japanese imperial year
• Jikkan Jūnishi (sexagenary cycle)
• Regnal name
• Regnal years worldwide
• Related systems:
  • Chinese era name
  • Korean era name
  • Vietnamese era name

• Bramsen, William. (1880).Japanese Chronological Tables: Showing the Date, According to the Julian or Gregorian Calendar, of the First Day of Each Japanese Month, from Tai-kwa 1st year to Mei-ji 6th year (645 AD to 1873 AD): with an Introductory Essay on Japanese Chronology and Calendars. Tokyo: Seishi Bunsha.OCLC 35728014.
• Brown, Delmer M.; Ishida, Ichirō, eds. (1979).The Future and the Past: a translation and study of the Gukanshô, an interpretative history of Japan written in 1219. Berkeley, CA: University of California Press.ISBN 978-0-520-03460-0.OCLC 251325323.
• Daijirin, 2nd edition.
• Daijisen, 1st edition.
• Kōjien, 5th edition.
• Murray, David (1894).The Story of Japan. New York: G.P. Putnam's Sons.OCLC 1016340.
• NengoCalc. Online conversion of Japanese dates into their Western equivalents; calculation is based on tables fromTsuchihashi (1952) andZöllner (2003).
• Nussbaum, Louis-Frédéric (2005).Japan encyclopedia. Translated by Käthe Roth. Cambridge:Harvard University Press.ISBN 978-0-674-01753-5.OCLC 58053128.
• Ponsonby-Fane, Richard. (1959).The Imperial House of Japan. Kyoto: Ponsonby Memorial Society.OCLC 194887
• Titsingh, Isaac (1834).Nipon o daï itsi ran: ou Annales des empereurs du Japon (in French). Translated byTitsingh, Isaac. Paris: Royal Asiatic Society, Oriental Translation Fund of Great Britain and Ireland.OCLC 5850691.Nihon Ōdai Ichiran
• Tsuchihashi, Paul Yashita (1952).Japanese chronological tables from 601 to 1872 (邦曆西曆對照表: 自推古九年至明治五年,Hōreki seireki taishōhyō: Suiko kyūnen yori Meiji gonen ni itaru) (in Japanese). Tokyo: Sophia University.OCLC 001291275.
• Varley, H. Paul (1980).Jinnō Shōtōki: A Chronicle of Gods and Sovereigns. New York: Columbia University Press.ISBN 978-0-231-04940-5.OCLC 59145842.
• Zöllner, Reinhard (2003).Japanische Zeitrechnung: ein Handbuch. Munich: Iudicium Verlag.ISBN 9783891297834.OCLC 249297777.
• 二中歴1 第一～第四（尊経閣善本影印集成）ISBN 4-8406-2314-7.
• 二中歴2 第五～第十（尊経閣善本影印集成）ISBN 4-8406-2315-5.
• 二中歴3 第十一～第十三（尊経閣善本影印集成）ISBN 4-8406-2316-3.
• 所功, (1977). 日本の年号　揺れ動く＜元号＞問題の原点. 雄山閣.
• 井上清, (1989). 元号制批判 やめよう元号を. 明石書店.ISBN 4-7503-0236-8.

• Nengō converter

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