Nengō: The Japanese Era Name

The Japanese calendar scheme is identified by two elements: the first is nengō or gengō (the Japanese era name) and the second is a number that indicates the number of years since an era began.

The nengō system was derived from the Chinese Imperial practice that dates back to 140 B.C.E. and was also common practice in East Asia. It was adopted by Japan in 645 C.E. during the reign of Emperor Kōtoku. The very first era name that was assigned was “Taika” which celebrated the political organizational changes from the great Taika Reform Edicts (set of doctrines established by Emperor Kōtoku). The regular practice of proclaiming era names was interrupted in the late 7th century but was reinstated in 701 during Emperor Mommu’s reign (697–707). Since then, era names have been used continuously: Japanese government offices usually require era names and years on official papers.

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Timeline of Japanese era names. (click images to enlarge)

Before the Meiji period, era names were chosen by court officials and were subjected to frequent change: a new era name might change within a year or so after the ascension of a new emperor. A new era name was often designated as well on the first (kakurei), fifth (kakuun), and 58th (kakumei) years of the sexagenary cycle (a cycle of 60 terms used for recording days or years) because they are believed to be inauspicious years in Onmyōdō (a traditional Japanese esoteric cosmology). They are collectively known as sankaku.

In historical practice (pre-Meiji period), the first day  of nengō  begins whenever the emperor wishes it to start, with the first year continuing on until the next lunar new year which marks  the beginning of nengō’s second year. In modern times, the first year of nengō starts as soon as the Emperor ascends the throne and end on December 31. The succeeding years follow the Gregorian calendar.

Emperor Akihito

The current era in Japan is Heisei. It began on the 8th of January 1989, the very first day after the death of the then reigning Emperor, Hirohito. He was succeeded by his son Akihito and in accordance with Japanese customs, Hirohito was posthumously renamed “Emperor Shōwa” on the 31st of January 1989. The four era names used since the end of the Edo period in 1868 can be abbreviated by taking the first letter of the Romanized names. (For example, Shōwa 55, S55, is 1980 C.E. or Heisei 22, H22 is 2010 C.E.) To covert a Western year after 1989 to Heisei era, simply subtract 1988 to any year after it (i.e. for 2015, 2015-1988= Heisei 27).

Emperor Akihito.