《宋书·志·卷十二》
推算太阳、月亮在昏、明时位置的方法说：对太阳用纪法，对月亮用月周乘以与所求日期最接近的节气的夜漏刻数，再除以二百，其商就是明分。
推日月昏明度术曰：日以纪法，月以月周，乘所近节气夜漏，二百而一，为明分。
The method for calculating the positions of the sun and the moon at dusk and dawn: for the sun use the epoch, for the moon use the moon's cycle multiplied by the number of hours between sunset and the closest term to the date in question, divide it by two hundred, and the result is the bright digit.