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Overview
Key data
| Item | Detail |
|---|---|
| Period of use | 443 – 462 CE |
| Compiler | He Chengtian |
| Innovation | The tiaori fa |
| Year head | Jian-yin |
He Chengtian and the Yuanjia calendar
The Yuanjia calendar was made by He Chengtian of the Liu Song and promulgated in 443 CE; it was used until 463 CE. He was learned in calendrical reckoning as well as in music and history, a scholar of wide range.
The tiaori fa
Calendrical work often has to express a measured quantity as a fraction between a “strong” and a “weak” rate. The tiaori fa takes the two and blends them, by proportional adjustment, into a fraction of the needed precision — approaching the true value by adjusting intermediate terms.
The method was general among later calendrists and was a systematic treatment of rational approximation in the calendar, of note in the history of mathematics as well.
Other work
He Chengtian also argued against the long “grand epoch” reckoning, preferring to start from a near, measured epoch; though not adopted then, the idea was taken up after the Tang.
From the Han on, calendrists increasingly worked from measurement: to reform a calendar one first measured the gnomon and the stars against the old methods.
Full text
No electronic full text of this work is available here. This calendar has no separate transmitted text; its methods survive scattered in the calendrical treatises of the standard histories. Among the histories held here, see Songshu, Calendrical Treatise, juan 13.
The title, date, summary and index structure compiled here are offered under CC BY 4.0 (attribution: Chujia Kuang · kuangchujia.com).
Compiled and arranged by Chujia Kuang.