This collection is estimated to have been compiled during the Kohei era when Akihira was appointed to a number of important posts, such as Monjo hakase (professor of literature) and Togu hakase (professor for the crown prince) in his later years.
成立した年代については、明衡が文章博士や東宮博士の要職に就いた晩年期の康平年間ではないかと推定されている。