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Overview
Key data
| Item | Detail |
|---|---|
| Period | Sui (604–617) |
| Compiler | Liu Zhuo |
| Tropical year | 365.2445 days |
| Precession | One degree in 75 years |
Liu Zhuo and the Huangji calendar
The Huangji calendar was made by Liu Zhuo of the Sui, the foremost calendrist of the age. Though never formally promulgated, its methods were taken up by the Tang Dayan calendar and others, with lasting effect.
Three innovations
1. The method of the true solar term (dingqi). Terms were divided by the sun’s actual position rather than by equal time — dingqi against pingqi — and used to compute the sun’s place.
2. Second-order interpolation at equal intervals. Since the sun’s motion is uneven, Liu used a second-order interpolation to find its position at any moment — an early use of interpolation in the calendar.
3. Precession at one degree in 75 years, adjusted after Zu Chongzhi and closer to the truth.
A calendar never promulgated
Blocked by the powerful, it was never promulgated and served only for computing eclipses.
That an unpromulgated calendar should deeply influence those that followed is rare — evidence that merit is not lost by a temporary rejection.
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 Suishu, Calendrical Treatise, juan 17.
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.