Glossary

one reign, one era

一世一元

Term · calendar

The rule, in Japan since 1868, that an emperor reigns in a single era — after his death he is called by its name (Emperor Meiji, Emperor Shōwa). One reign, one era (一世一元, issei ichigen): since the decree of 1868 that made Meiji the era of the new emperor, Japan changes its era name (nengō) only when an emperor comes to the throne. The era and the reign are one; after his death the emperor is known by the name of his era — Emperor Meiji, Emperor Taishō, Hirohito as Emperor Shōwa. The rule was written into law with the Era Name Act of 1979. Since an abdication ended the Heisei era in 2019, Akihito is alive while his era is closed; Reiwa is that of Naruhito. The rule follows the Ming and Qing emperors of China, who also kept one era each and are known by it (the Qianlong Emperor; see nianhao).