Japanese era name

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

Era names originated in 140 BCE in Imperial China, during the reign of the Emperor Wu of Han. As elsewhere in the Sinosphere, the use of era names was originally derived from Chinese imperial practice, although the Japanese system is independent of the Chinese, Korean, and Vietnamese 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 the Edo period in 1868 can be abbreviated by taking the first letter of their romanized 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.

The Reiwa (令和) era began on 1 May 2019, the day of accession of Naruhito to the throne as the 126th Emperor of Japan, following the day of the planned and voluntary abdication of his father, the 125th Emperor, Akihito. Emperor Akihito had received special permission to abdicate, rather than serving in his role until his death, as is the rule. The Reiwa (令和) era followed the 31st and final year of the Heisei era (平成31年), which had started on the day after the death of Emperor Hirohito on 8 January 1989.

Overview


The system on which the Japanese era names are based originated in China in 140 BC, and was adopted by Japan in 645 AD, during the reign of Emperor Kōtoku.

The first era name to be assigned was "Taika" (大化), celebrating the political and organizational changes which were to flow from the great Taika 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.

Historical nengō
Prior to the Meiji 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 the sexagenary cycle, because they were inauspicious years in Onmyōdō. These three years are respectively known as kakurei, kakuun, and kakumei, and collectively known as sankaku. Era names were also changed due to other felicitous events or natural disasters.

In historical practice, the first day of a nengō (元年) 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.

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 in Chichibu. Most nengō are composed of two kanji, except for a short time during the Nara 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 the Heian period, Confucian thoughts and ideas have been reflected in era names, such as Daidō (大同), Kōnin (弘仁) and Tenchō (天長). 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, Oei, Meiji, and Showa have been used for more than 30 years.

Nengō in modern Japan
Mutsuhito assumed the throne in 1867, during the third year of the Keiō (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) 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 the Ming dynasty. The Japanese nengō system differs from Chinese practice, in that in the Chinese system 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) starts immediately upon the emperor's accession and ends on 31 December. Subsequent years follow the Gregorian calendar. For example, the Meiji era lasted until 30 July 1912, when the Emperor died and the Taishō (大正) era was proclaimed. 1912 is therefore known as both "Meiji 45" and "Taishō 1" (大正元年), 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). 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). It is protocol in Japan that the reigning emperor be referred to as Tennō Heika (天皇陛下) or Kinjō Tennō (今上天皇). To call the current emperor by the current era name, i.e. "Reiwa", even in English, is a faux pas, as this is – and will be – his posthumous name. Use of the emperor's given name (i.e., "Naruhito") is rare, and is considered vulgar behaviour in Japanese.

The Emperor Akihito abdicated on 30 April 2019, necessitating a change in nengō. The new name, made public on the morning of 1 May of the same year, is Reiwa (令和).

Periods without era names
The era name system that was introduced by Emperor Kōtoku was abandoned after his death; no era names were designated between 654 and 686. The system was briefly reinstated by Emperor 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 the Gregorian 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.

Although in modern Japan posthumous imperial names correspond with the eras of their reign, this is a relatively recent concept, introduced in practice during the Meiji 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 which Emperor Bidatsu assumed the Chrysanthemum 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. 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.

Unofficial era name system
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 called shinengō (私年号), also known as ginengō (偽年号) or inengō (異年号). Currently, there are over 40 confirmed shinengō, most of them dating from the middle ages. Shinengō used prior to the reestablishment of the era name system in 701 are usually called itsunengō (逸年号).

Because official records of shinengō 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 the Hakuchi era. However, alternate interpretations exist. For example, in the Nichūreki, 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-known itsunengō and shinengō 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 recent shinengō is Seiro (征露) (1904–1905), named for the Russo-Japanese War.

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

Character sets
Certain era names have specific characters assigned to them, for instance ㋿ for the Reiwa period, which can also be written as 令和. These are included in Unicode: 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.

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

Since the release of Java 8, the Japanese calendar is supported in the new Date and time API for the year Meiji 6 (1873) onwards.

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

Unicode code point U+32FF (㋿) was reserved for representing the new era name, Reiwa.

The list of Japanese era names is the result of a periodization system which was established by Emperor Kōtoku in 645. The system of Japanese era names (年号) was irregular until the beginning of the 8th century. After 701, sequential era names developed without interruption across a span of centuries. As of 1 April 2019, there have been 239 era names.

List of Japanese era names
To convert a Japanese year to a Gregorian calendar year, find the first year of the Japanese era name (also called nengō). When found, add the number of the Japanese year, then subtract 1.

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

Non-nengō periods
Unofficial non-nengō periods (shinengō) before 701 are called itsunengō (逸年号). Pre-Taika chronology intervals include:
 * Reign of Emperor Jimmu, 660–581 BC
 * Reign of Emperor Suizei, 581–548 BC
 * Reign of Emperor Annei, 548–510 BC
 * Reign of Emperor Itoku, 510–475 BC
 * Reign of Emperor Kōshō, 475–392 BC
 * Reign of Emperor Kōan, 392–290 BC
 * Reign of Emperor Kōrei, 290–214 BC
 * Reign of Emperor Kōgen, 214–157 BC
 * Reign of Emperor Kaika, 157–97 BC
 * Reign of Emperor Sujin, 97–29 BC
 * Reign of Emperor Suinin, 29 BC–AD 71
 * Reign of Emperor Keikō, AD 71–131
 * 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
 * Reign of Emperor Jomei, 629–645

Post-Taika chronology intervals not covered by the nengō system include:
 * Reign of Empress Saimei, 655–662 ... Saimei (period)
 * Reign of Emperor Tenji, 662–672 ... Tenji (period)
 * Reign of Emperor Kōbun, 672–673 ... Kōbun (period) or Sujaku (or Suzaku)
 * Reign of Emperor Tenmu, 673–686 ... Tenmu (period) or Hakuhō period
 * Reign of Empress Jitō, 687–697 ... Jitō (period)
 * Reign of Emperor Monmu, 697–701 ... Monmu (period)