Japanese Era Name - Periods Without Era Names

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 Temmu in 686, but was again abandoned upon his death approximately two months later. In 701, Emperor Mommu 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, 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. 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 through today.