However, concerning more specific timing, there are many theories depending on the documents, as in the following: in the reign of Emperor Nijo, that of Emperor Konoe, that of Emperor Goshirakawa and that of Emperor Toba.
しかしながら、平安時代のいつ頃かは、二条天皇の時代、近衛天皇の時代、後白河天皇の時代、鳥羽天皇の時代など、資料によって諸説ある。