论中国古代的第三种日界——以陕西出土的西魏北周造像碑为例

The Third Kind of Date Line in the Ancient China:An Example of the Statue Monuments During Western Wei and Northern Zhou Dynasties Unearthed in Shaanxi Province

日界是指划分日的界线。中国古代传统历法通常使用夜半和平旦作为干支日的分界线。将陕西出土的西魏北周时期佛教造像碑所记的干支信息与《二十史朔闰表》《三千五百年历日天象》等工具书进行查对,发现朔日干支与所在月份存在不合现象,表现为干支序号差一。再以南北朝时期官方行用的《景初历》《大明历》《正光历》进行推算,结果表明:凡是朔日干支序号数进一的都是朔小余大于0.8的情况,也就是当合朔时刻在昏之后,造像碑上的朔日干支就会使用下一日的日名干支。因此,昏可以被认为是中国古代除夜半和平旦之外的第三种日界。

The date line refers to the boundary of the time that determines the beginning of the civil day numbered in order by Gan-Zhi(干支,Heavenly Stems and the Earthly Branches).In the traditional Chinese calendar,the two moments were used as the date line,which is midnight(夜半)and daybreak(平旦).However,comparing the date recorded on the Buddhist statues monuments,which is unearthed in the Shaanxi area during the Western Wei and Northern Zhou dynasties,and some reference books and tables,we notice that there is a one shift of the ordinal number of the first day of the lunar month in some cases.In order to explain it,we calculate by the Jingchu-Li,Daming-Li,and the Zhengguang-Li,which are three official calendars used in the Southern and Northern Dynasties,and then find that if the time between the new moon and the previous midnight is greater than 0.8 days,the ordinal number Gan-Zhi of the day will be increased by one.In other words,when the time of the new moon is after the evening(昏),the name of the date on the monument will use the name of Gan-Zhi of the next day.Therefore,the evening can be regarded as a new kind of date line in ancient China besides midnight and daybreak.