It was impossible to know when the Kobunin was founded mainly because "Nihon Koki" was scattered and ultimately lost; but from the other records of Hiroyo, it was estimated that the Kobunin was founded from the end of the Enryaku era (782 - 806) to the beginning of the Daido era (the first year of Daido was 806).
弘文院設立の時期は『日本後紀』の散逸などにより不明であるが、広世に関する他の記事から延暦年間末期から大同(日本)年間初頭（大同元年は806年）の設立と推定されている。