The Japanese era calendar scheme is a common calendar scheme used in Japan, which identifies a year by the combination of the Japanese era name (年号 nengō?, lit. year name) and the year number within the era. For example, the year 2006 is Heisei 18, and 2007 is Heisei 19.

As elsewhere in East Asia, the use of nengō, also known as "gengō" (元号?), was originally derived from Chinese Imperial practice, although the Japanese system is independent of the Chinese, Korean and Vietnamese era-naming systems. Unlike these other similar systems, Japanese era names are still in use. Government offices usually require era names and years for official papers.

Sometimes an era name is expressed with the first letter of the romanized name. For example, S55 means Shōwa 55. At 64 years, Shōwa is the longest era to date.


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

The first nengō 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?). Although the regular practice of proclaiming successive nengō was interrupted in the late seventh century, it was permanently re-adopted in 701 during the reign of Emperor Mommu (697-707). Since then, era names have been used continuously up through the present day.[1]

Historical nengō[]

Prior to the Meiji period, era names were decided by court officials and were subjected to frequent change. A new nengō was usually proclaimed within a year or two after the ascension of a new emperor. Besides changes in imperial reign, a new nengō was also normally designated at two points in each sexagenary cycle (the first and the 58th years), because these years were considered to be auspicious according to the Chinese astrological principles. Era names were also changed due to other felicitous events or natural disasters.

In historical practice, the first day of 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.[2]

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 comprised 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 247 Japanese era names, only 72 kanji have been used in composing them. Out of these 72 kanji, 30 of them have been used only once, while the rest have been used repeatedly in different combinations.

Nengō in modern Japan[]

Mutsuhito assumed the throne in 1867, during the third year of the Keiō (慶応?) era. On Sept. 8, 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 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 reign (元年 gannen) starts immediately upon the emperor's ascension to the throne and ends on December 31st. Subsequent years follow the Gregorian calendar.

For example, the Meiji era lasted until July 30th, 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 Taishō gannen?), although Meiji technically ended on Jul. 30th 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 four era names assigned: Meiji, Taishō, Shōwa and Heisei, 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?).

NB: It is protocol in Japan that the reigning emperor should be referred to as Tennō Heika (天皇陛下, "His Majesty the Emperor") or Kinjō Tennō (今上天皇, "current emperor"). To call the current emperor by the current era name, i.e. "Heisei", 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., "Akihito") is rare in Japanese.

Conversion table from nengō to Gregorian calendar years[]

To convert a Japanese year to a Western or Gregorian calendar year, find the first year of the nengō (the nengō = the era name, see list below). When found, subtract 1, and add the number of the Japanese year. For example, the 23rd year of the Showa Era (Showa 23) would be 1948:

ILLUSTRATION: 1926 1 1925 ..., and then 1925 + 23 1948 ... or Showa 23.

Non-nengō periods[]

The nengō system that was introduced by Emperor Kōtoku was abandoned after his death; no nengō were designated between 654 and 686 CE. The system was briefly reinstated by Emperor Temmu in 686 CE, but was again abandoned upon his death approximately two months later. In 701 CE, Emperor Mommu once again reinstated the nengō system, and it has continued uninterrupted through today.

Although use of the Gregorian calendar for historical dates has become increasingly common in Japan, the traditional Japanese system demands that dates be written in reference to nengō. The apparent problem introduced by the lack of nengō for the two periods above is resolved by referencing years of imperial reign. This is the same approach used when referencing periods that predate the introduction of the nengō system.

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, 572 CE—in which Emperor Bidatsu assumed the Chrysanthemum Throne—is properly written as "敏達天皇元年" (Bidatsu-Tennō Gannen, lit. "the first year of Emperor Bidatsu"), and not "敏達元年" (Bidatsu Gannen, lit. "the first year of Bidatsu"), although it may be abbreviated as such.[1] 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.[2]

The following is an example of such an extension of the nengō system to include the post-Taika years not covered by a proper era name:

Imperial year[]

Kōki (皇紀), or Imperial year, is an epoch used before WW2. Kōki 1 is the year when Emperor Jimmu founded Japan, that is 660 BC. This epoch system was adopted in 1872. In terms of nationalism, Kōki emphasizes the long history of Japan and imperial family because it is a bigger number than Anno Domini.

Kōki 2600 (AD 1940) was a special year. 1940 Summer Olympics and Tokyo Expo were planed as anniversary events, but canceled due to Second Sino-Japanese War.

After the Second World War, the United States occupied Japan, and stopped the use of Kōki by officials. Today, Kōki is rarely used.

Unofficial nengō system[]

In addition to the official nengō 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, mostly seen in Nichūreki(二中歴), a 12th century work. most of them dating from the middle ages. Shinengō used prior to the reestablishment of the nengō system in 701 CE are usually called itsunengō (逸年号?). A list of shinengō and more information can be seen in the Japanese wikipedia page ja:私年号. Some of the shinengō were proposed to be the Kyūshū nengō(九州年号), a controversial hypothesis of an official era name system used by another kingdom in the Kyushu island in old time. Lists of the proposed Kyūshū nengō can be seen in the Japanese wikipedia pages ja:鶴峯戊申 and ja:九州王朝説.

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 middle-age 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 CE), Fukutoku (福徳?) (1489-1492 CE), Miroku (弥勒?) (1506-1507 CE or 1507-1508 CE) and Meiroku (命禄?) (1540-1543 CE).

The most recent shinengō is Seiro (征露?) (1904-1905 CE), named for the Russo-Japanese war.


  1. ^ Brown, Delmer. (1979). Gukanshō, p.32.
  2. ^ Ponsonby-Fane, Richard. (1956). Kyoto: the Old Capital of Japan, 794-1869, p. 321. [Example: Hōreki (1751-1761), meaning "Valuable Calendar, is proclaimed retroactively by Emperor Momozono in 1754.]

See also[]

External Timeline
A graphical timeline is available here:
Timeline of Japanese era names

External links[]

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