Interregnum - Japanese Era Names

Japanese Era Names

While not describing true interregna, the Japanese era name or nengō system which was introduced in reign of Emperor Kōtoku was abandoned at the end of his reign, thus resulting in sitting emperors without era names; these era names were not updated for some time, except for a very brief re-occurrence near the close of Emperor Temmu's reign.

During the nearly half-century after Emperor Kōtoku, the reigning sovereigns were

• Saimei-tennō (斉明天皇)
• Tenji-tennō (天智天皇)
• Kōbun-tennō (弘文天皇)
• Temmu-tennō (天武天皇)
• Jitō-tennō (持統天皇)
• Mommu-tennō (文武天皇).

The first year of Emperor Mommu's rule (文武天皇元年; 686) could be arguably abbreviated as "the first year of Mommu" (文武元年; 686), but this is nowhere understood as a true era name. The reigns of Japanese emperors and empresses were not considered to also be the same as the era name until the Meiji era. References to the emperors of Japan who ruled during this period are properly written as, for example, "the 3rd year of Emperor Mommu" (文武天皇３年; Mommu is the emperor's name, not that of the era), and not "the 3rd year of Mommu" (文武３年; this second writing implies that Mommu is the era name).

The two periods in the pre-Taihō years without era names are 654 (the end of the Hakuchi era) through 686 (the reinstatement of the Shuchō era), and again from 686 (the Shuchō era) to 701 (some time in the middle of the reign of Emperor Mommu), when the Taihō era was declared and nengō reinstated.