From the viewpoint of political history, the preceding Middle Japanese corresponds to the insei period (during the period of the government by the retired Emperor) at the end of the Heian period to the Kamakura period, and the latter Middle Japanese to the Muromachi period.
政治史で見ると前期中世日本語は平安時代末の院政期から鎌倉時代、後期中世日本語は室町時代に相当する。