Cao Shi-yi (English spelling)

Japanese: 曹士蔿 - そうしい（英語表記）Cáo Shì wěi

An astronomer from the Tang Dynasty in China. Dates of birth and death unknown. He served as Da Zhong Daifu (Great Middle Minister) for a number of years, and during the Jianzhong era (780-783) compiled the Futen Calendar, which replaced the traditional calendar system. He abolished the Shangyuan accumulated years method and used the near-distance method, which took the rainwater of 660 (Xiangye 5) as the starting point of the calendar, and introduced the Manbun method, which takes one tropical year as 365 days + 2448/10,000 days. These methods were adopted in the Chogen calendar of the Five Dynasties and the Shushi calendar of the Yuan Dynasty. The positions of the nine stars (the sun, moon, five stars, Rahu, and Keito) were calculated and used in astrology. The Futen calendar was not adopted by the official calendar and was looked down upon as a small calendar, but it was widely used among the general public, and was imported to Japan and used by Shukuyo masters.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

中国，唐代の天文学者。生没年不詳。大中大夫を歴任し，建中年間(780‐783)に従来の暦法をかえて《符天暦》を編んだ。上元積年の法を廃止して660年(顕慶5)の雨水を暦元とする近距法を用い，1回帰年を365日＋2448/10000日とする万分法を導入したもので，こうした方法は五代の調元暦，元の授時暦に採用された。九曜(日月五星と羅睺（らご），計都)の位置が計算され，占星術に使われた。符天暦は官暦には採用されず小暦と卑しめられたが，民間では広く行われ，日本にも輸入されて宿曜師が用いた。

出典　株式会社平凡社世界大百科事典第２版について　情報

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