Astrologer
Sima and his father were both court astrologers (taishi) 太史 in the Former Han Dynasty. At that time, the astrologer had an important role, responsible for interpreting and predicting the course of government according to the influence of the Sun, Moon, and stars, as well as other phenomena such as solar eclipses and earthquakes.
Before compiling Shiji, in 104 BC, Sima Qian created Taichuli (太初曆, which can be translated as 'The first calendar') on the basis of the Qin calendar. Taichuli was one of the most advanced calendars of the time. The creation of Taichuli was regarded as a revolution in the Chinese calendar tradition, as it stated that there were 365.25 days in a year and 29.53 days in a month.
The minor planet 12620 Simaqian is named in his honour.
Read more about this topic: Sima Qian