Japanese era
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Japanese_era".

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 2008 is Heisei 20.

As elsewhere in East Asia, the use of nengō, also known as "gengō" (元号, "gengō"^?), 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 (i.e. 1980 A.D.). At 64 years, Shōwa is the longest era to date.

Overview

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, "Taika"^?), celebrating the political and organizational changes which were to flow from the great Taika reform (大化の改新, Taika reform^?). 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. A new nengō 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 (革令, kakurei^?), kakuun (革運, kakuun^?), and kakumei (革命, kakumei^?), and collectively known as sankaku (三革, 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, 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, Wadō^?), 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 Kanpō^?), Tenpyō Shōhō (天平勝宝, Tenpyō Shōhō^?), Tenpyō Hōji (天平宝字, Tenpyō Hōji^?) and Tenpyō Jingo (天平神護, Tenpyō Jingo^?) 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, Daidō^?), Kōnin (弘仁, Kōnin^?) and Tenchō (天長, Tenchō^?).^{citation needed} 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, Keiō^?) era. On Oct. 23, 1868, the era name was changed to "Meiji" (明治, "Meiji"^?), 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 nengō (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, Taishō^?) 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 Gregorian calendar years to nengō

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.