Chapter 40 Section 5 Change point system

The more point system was very popular in ancient China.In ancient times, almost every county had a drum tower for beating drums to tell the time.When it comes to a little more system, almost everyone knows that it is used to tell the time at night.But if you ask why in ancient China, the fifth watch was used to record the time at night?When is the beginning and end of the fifth watch?Even how to calculate the fifth watch?Many people may not be able to tell clearly. The Five Watches of ancient China started very early.In the "Han Jiuyi" of the Han Dynasty, there are records of Jia Ye, Yi Ye, Bing Ye, Ding Ye, and Wu Ye. There is a record of "Bingye Yichou" in "Book of Jin", and "Bingye Yichou" is the third watch of later generations. It can be seen that the Jin Dynasty already had a watch system. "Sui Shu Astronomical Records" said when recalling the pre-Qin leaks: "In the daytime there are Chao, Yu, Zhong, Asr, and Xi, and at night there are A, B, C, D, and E." It seems that there were in the pre-Qin period A system that divides the day and night into 10 periods, with five periods each for day and night.

The "Essentials of the Five Classics" of the Han Dynasty said: "Three quarters after the sun sets, it is dark, and three quarters before sunrise is bright." This is the definition of dun in the Western Han Dynasty, which was later changed to two and a half quarters. "Book of Tang" records that "adding the sun to the hour at dusk, you get the first moment of Jiaye", which shows that the fifth watch finally begins at dusk.It can be seen from this that if we divide each night into five shifts and divide each shift into five points, we only need to divide the night time by five to get each shift time, and then divide each shift time by five to get each shift time. Take a moment.Since the length of day and night changes with the seasons, every ancient calendar has a timetable for each solar term at dusk for people to calculate a better time.

After understanding the reason that the time of night changes with the seasons, we can know that the time of each watch is not fixed.So some books say that one watch is equal to two hours, which is not accurate.The calculation shows that the winter solstice is 11 quarters, the summer solstice is 7 quarters, and the rest of the seasons are between these two quarters.Each point is also between 20 minutes and 30 minutes.