Because the private possession of rekisho (explanatory books concerning calendars) was strictly regulated by Hishogenjo-rei edicts, which were classified as Zoryo (Law on Miscellaneous Matters), it was difficult to recruit personnel outside the Imperial Court; therefore, when TAIRA no Masakado proclaimed himself as a 'new emperor' and nominated Bunbu Hyakkan (all the officials, both military and civil), he was unable to appoint Reki Hakase, and in the same manner the Yoshino Imperial Court (the Southern Court (Japan)) was unable to appoint Reki Hakase, and consequently there is no Guchu-reki (annotated calendar) that includes its gengo (era name).
なお、暦書を私的に持つことは雑令の秘書玄象令で厳しく規制されたために朝廷外に人材を求めるのは困難であり、平将門が「新皇」を名乗って文武百官を任じた際も暦博士は任命できず、同様に吉野朝廷（南朝(日本)）も暦博士を置けなかったらしく、その元号が入った具注暦は存在しない。