Tongyuan Calendar

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Overview

Key data

Reform after the move south

With the Southern Song established, the Tongyuan calendar was promulgated in 1135, made by Chen Deyi. After the court moved south books and instruments were scattered, and precision suffered for a time.

It was used until 1160. The Southern Song changed calendars often, as observing conditions were recovered.

Its relation to the Northern Song calendars

The Tongyuan calendar continues the Jiyuan calendar of the Northern Song (used from the Chongning period),

its methods resting on Northern Song observation and computation. After the move south the books were scattered and the officials worked largely from damaged copies, so that precision fell short of the old Northern Song standard for a time.

The early Southern Song calendars — Tongyuan, Qiandao, Chunxi, Huiyuan, Tongtian — follow one another with repeated revision,

and the closeness of that succession is itself a feature of Southern Song calendrics.

Why reform came so often

Two causes are usually given for the frequency of reform in the Southern Song:

first, eclipse predictions repeatedly failed, and the officials were impeached for it; second, after the move south both observations and mathematical books were wanting, so that the old precision could not be recovered.

Reform being frequent, each calendar was used only briefly, and there was little chance to accumulate observation — a circle that fed itself.

That circle was broken only with Yang Zhongfu’s Tongtian calendar and its new value for the tropical year.

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 Songshi, Calendrical Treatise, juan 81.
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.