Lidai changshu jiyao 歷代長術輯要

Lidai changshu jiyao 歷代長術輯要 is a book on astronomy written during the late Qing period 清 (1644-1911) by Wang Yuezhen 汪曰楨 (1822-1882), courtesy name Gangmu 剛木, style Xiecheng 謝誠 or Xinfu 薪甫, from Wucheng 烏程 (today's Huzhou 湖州, Zhejiang). He was educational instructor (jiaoyu 教諭) of Guiji 會稽, Zhejiang. Wang compiled the local gazetteers Wucheng xian zhi 烏程縣志 and Nanxun zhen zhi 南潯鎮志. Among his scientific books are Taisui chaochen biao 太歲超辰表, Tuice xiaoshi 推策小識, Ruji yinmeng 如積引蒙 and Sisheng junyun biao buzheng 四聲均韻表補正. His collected writings are Suishan yufang chao 隨山宇方鈔, Yujiantang shicun 玉檻堂詩存, Liji shucun 櫟寄詩存 and the series Liqiang congke 荔墻叢刻.

The book of 10 juan length is included in the Liqiang congke and the series Sibu beiyao 四部備要.

During the high Qing period, the tradition of evidential scholarship (kaozhengxue 考證學, see Qian-Jia School) tradition flourished. The compilation and study of ancient Chinese astronomical records also entered a period of great activity. The research and organisation of these materials primarily focused on two aspects: one was the detailed study of astronomical records found in classical texts and historical annals, along with specific calendars; the other was a systematic and comprehensive examination of ancient Chinese calendrical systems as a whole. One of the earliest attempts at an exhaustive study of historical calendars was initiated by Mei Wending 梅文鼎 (1633-1721; see his Lisuan quanshu 曆算全書), who continued the work of Xing Yunlu's 邢雲路 (b. 1549) Gujin lüli kao 古今律曆考 and began compiling the Gujin lifa tongkao 古今曆法通考. Unfortunately, this work was never completed, and its contents are now lost. Li Rui 李鋭 (see Rifa shuoyu qiangruo kao 日法朔餘强弱考) also had ambitious plans for a similar undertaking. However, he only managed to complete annotations on three ancient calendars — the Santong 三統曆, Sifen 四分曆, and Qianxiang 乾象曆 calendars — along with partial annotations on the Fengyuan 奉元曆 and Zhantian 占天曆 calendars.

The scholar who ultimately accomplished this immense project was Wang Ruizhen with his Lidai changshu jiyao. He spent over 30 years compiling this work, which required extraordinary dedication. The completed book became a significant reference in astronomical calendrical studies and historical chronology. The work spans from the Gonghe era 共和 (841 BCE) of the Western Zhou period 西周 (11th cent.-770 BCE) to the latest official almanac Wannianshu 萬年書 issued by the Directorate of Astronomy (qintianjian 欽天監). For each year, it systematically records the intercalary months, the start of lunar months, their lengths, and the 24 solar terms, following a format similar to that of the Wannianshu. Additionally, the work includes two supplementary volumes, an examination of ancient astronomical computation methods (Gu han tuibu zhushu kao 古含推步諸術考), and chronological tables of the Sexagenary Cycle (Jiazi jiyuan biao 甲子紀元表), bringing the total to 53 volumes. The book also includes inscriptions on long-term astronomical methods throughout the dynasties (Lidai changshu tici 歷代長術題辭) and a preface with tables of contents for the examination of Lunar and Solar dates in the 24 official dynastic histories (Ershisi shi yueri kao xumu 二十四史月日考序目).

In 1866, Mo Youzhi 莫友芝 (1811-1871) reviewed the work, feeling that its sheer volume was excessive. As a result, he abridged it, modelling the revision after the table of contents of the Tongjian gangmu 通鑒綱目, focusing primarily on recording new moons and intercalary months. He also appended notes at the end of each year listing discrepancies found in other historical sources. This condensed version was reduced to 10 volumes and was completed in 1867.

The main text covers all historical periods. It concludes in 1670, after which it provides a detailed study of the Wannianshu.

In his work, Wang Ruizhen systematically arranged the officially used calendars in chronological order. He conducted critical astronomy examinations on the time before the introduction of the Taichu Calendar 太初曆 (104 BCE) and provided discussions on later calendars whenever doubts or clarifications were necessary. The core content of his tables focuses on two key elements: new moons (shuo 朔) and intercalary months (run 閏) — the fundamental aspects of all historical Chinese calendars. While seemingly simple, determining these two elements was a challenging task. After considering the complexities of historical calendrical records, two overarching difficulties emerge: the frequent inconsistencies and errors in ancient records and the disorderliness of calendrical systems across different dynasties. Yet, in reality, the challenges likely far exceeded these seven difficulties. Wang's research involved cross-referencing hundreds of historical sources, an effort that demanded both extensive time and painstaking labour. Beyond the sheer effort of gathering materials, evaluating and verifying the accuracy of calendrical data required exceptional analytical skill and intellectual rigour.