Index to Laws in Japan, run by the National Diet Library, mentions that the imperial decree of the practice of assigning one era name to the reign of each Emperor was lost its effectiveness by the Era Name Law which was established in 1979.
国立国会図書館が運営する日本法令索引では、1979年に元号法制定によって一世一元の詔は実効性喪失と記載している。