The following two figures are well-known as Reki Hakase: OKASUGA no Manomaro, who in the reign of the Emperor Seiwa advocated the introduction of Goki reki (Wuji calendar, a lunar-solar calendar developed in the Tang by Guo Xianzhi and used in China during the years 762 to 821) and Senmyo reki (a variation of the lunar calendar that was created in ancient China); and KAMO no Tadayuki, believed to be the sixth generation descendant of KIBI no Makibi, who brought the Taien calendar to Japan.
清和天皇の頃に五紀暦・宣明暦の導入を主唱した大春日真野麻呂や大衍暦を日本に持ち帰った吉備真備の6代目の子孫とされる賀茂忠行が良く知られた。