Tang Kaiyuan zhanjing 唐開元占經

Da-Tang Kaiyuan zhanjing 大唐開元占經 "Classic of astrology from the Kaiyuan reign-period of the Tang era" 唐 (618-907), shortly called Kaiyuan zhanjing 開元占經, is an astrological text attributed to a writer called Gautama Siddha (Chinese transliteration Qutan Xida 瞿曇悉達), whose ancestors hailed from India. During the reign of Emperor Xuanzong 唐玄宗 (r. 712-755), he served as Supervisor of the Directorate of Astrology (taishijian 太史監) and in 718, transposed the Indian Buddhist calendar on the Chinese calendric model. This calendar was called the Jiuzhi Calendar 九執曆.

The 120-juan-long Kaiyuan zhanjing is a vast compendium of the Chinese calendar. It begins with a description of ancient theories on the universe (juan 1-2). The first part of the book (juan 3-90) is a history of astronomy and astrology in China. It includes a list of many stars and can be compared with other lists like that of Shi Kun 石申, Gan De 甘德 and Wu Xian 巫咸 that are to be found in the book Gan-Shi xingjing 甘石星經.

The second part (juan 91-102) explains concrete methods of divination based on meteorological and astronomical phenomena. The books ends with a reproduction of Li Chunfeng's 李淳風 book Linde lijing 麟德曆經 (juan 103), a description of mathematical operations to calculate the calendar (juan 104), the application of these 29 methods to the historical calendars in Chinese history (juan 105), a large number of maps of the starry sky (juan 106-110, today lost), and explanations of several other divination methods related to the animal realm.

The Kaiyuan zhanjing is an extremely important book that includes much information on the traditional Chinese methods of combining astronomy with astrology. It quotes vastly from a lot of ancient books that are otherwise lost, especially because most of these texts were later rated as apocryphal and non-orthodox, like Zhang Heng's 張衡 (78-139) texts Linxian 靈憲 or Huntianyi tuzhu 渾天儀圖注. Modern Chinese scholars are especially critical towards the miscellaneous character especially of the latter part of the Kaiyuan zhanjing that has no relation to the realm of astronomy, like fortune-telling from the appearance of certain irregular phenomena in the world of plants and animals, or based on phenomena of the weather. Yet seen from the book title, it is well justified that the author surpassed the frame of divination by stars, sun and moon and described methods to prognosticate the future by other celestial or earthly phenomena. The Kaiyuan zhanjing can thus be seen as an early encyclopaedia on the art of divination by various methods.

After the Tang period the Kaiyuan zhanjing was lost, but in 1616 Cheng Mingshan 程明善 from Shexian 歙縣, Anhui, discovered a manuscript hidden inside a Buddha statue.

The Tang Kaiyuan zhanjing is included in the series Siku quanshu 四庫全書. In 1989 the Zhonghua Shudian Press 中國書店 has published a separate facsimile of this edition. An separate edition was printed during the Daoguang reign-period (1821-1850) by the Hengde Studio 恒德堂.