TENG Yan-hui1, TANG Quan2,3

(1. Research Center for the History of Mathematics and Science, Northwest University, Xi′an 710127, China;

2. School of Mathematics and Information Science, Xianyang Normal University, Xianyang 712000, China;

3. Institute of Chinese Ideology and Culture, Northwest University, Xi′an 710069, China)

Abstract: The time units and time units transformation in the ancient Chinese timing system are introduced. The measure and calculation of the basic astronomical constants such as the tropical year, and the determination and time service of the circadian time for the Song dynasty, which is an ancient historical period with flourishing science and culture, are discussed in detail. The calculation method of the time moment such as Qi, new-moon, mo and mie days, times of sunrise and twilight for the Song dynasty are analyzed combined with the calendars of the Song dynasty. Finally, it is pointed out that a complete time system, which comprises a time service system, an observations system for time measuring and a calendar system for time calculating, had been established in the Song dynasty.

Key words: time; the winter solstice; mo days; clepsydra