When it comes to late, people often say it's "late at night". Some people will question that it should be three and a half in the middle of the night at five o'clock? What's going on? It starts with the ancient time system.
Hour and meridian
It is a well-known fact that there are 24 hours a day. However, few people have thought about why it is 24 and why it is called "hour"? First, the number 24 is related to the hexadecimal of the time system. As early as 3000 BC, ancient Egypt divided the day and night into 12 parts. At that time, the sunrise was the beginning of the day. Babylon in Cuba is also bounded by sunrise, but the whole day is divided into 12 parts.
Chinese ancient traditions are different. China has always used "hour" to record the time of the day, with 12 hours a day. The 12 hours are named according to the order of earth branches. The first hour is called Zishi, which is roughly equivalent to 11 p.m. today to 1 a.m. the next day. Noon is called noon, which is equivalent to 11 a.m. to 1 p.m. In ancient China, when indicating the position, noon was due south and Zi was due north. Therefore, the longitude line running through the north-south direction is also called the meridian, and the meridian of Greenwich Observatory as the reference of international standard time is also called the primary meridian, that is, the 0 ° longitude.
Alias of hour
Speaking of hours and hours, they have another difference - their starting point is different. At midnight, it should be 0 or 24 o'clock. However, for the hour, the range of the first hour "Zishi" is from 23:00 to 1:00. It can be seen that the midnight is actually in the middle of the "Zishi". In other words, unlike ancient Egypt and ancient Babylon, a day in ancient China began at midnight. The advantage is that the transition between two days is completed in people's dreams, which makes timing more convenient.
Because of this feature, the ancients called the midnight as "Midnight", and the corresponding 12 hours also have other names. For example, the three hours before midnight are sunrise, dusk and rending, which means that the sun sets, the sky is dark and goes to bed. Three hours after midnight, it is called Chicken crowing, Pingdan and sunrise, which means that after midnight, the sky will be bright and the sun will rise. It can be seen that there are five hours between sunrise and sunrise. People give them another name, Wugeng, to calculate the night.
Five nights a night
The ancients turned one night into five watch, and from one watch to five watch corresponds to the five hours of dusk, rending, midnight, Jiming and Pingdan respectively. So far, we should understand why it is called Midnight - Midnight obviously corresponds to three watch. Strictly speaking, midnight is the middle of the third watch, which may be more accurate.
It is said that since the Han Dynasty, there has been the custom of "playing watch". The government appoints watchmen to patrol at night. According to the instructions of missing a quarter (water clock) at night, it also has the function of patrolling and duty. So people can sleep safely when they hear the watchman banging.
"Hour" and "hour"
In ancient China, a day was divided into 12 hours. Its name was taken from 12 branches: Zi, Chou, Yin, Mao, Chen, Si, afternoon, Wei, Shen, you, Xu and Hai. In the international standard 24-hour system, two hours is equivalent to one hour, exactly half, so it is called "hour".