How did you calculate years, months, and hours in ancient times? Please!

The cycle of cold and summer is one year, and the length of a year in the pre-Qin period was 365.25 days; the cycle of moon waxing and waning is a synodic month, and the length of a synodic month in the pre-Qin period was about 29.53 days. Year, month and day constitute the three basic elements of the calendar. The main task of the calendar is to reasonably arrange the three cycles of year, month, and day so that they become integers, which is not only easy to remember, but also easy to use.

There are three types of calendar compilation: one is the solar calendar that only considers the movement of the sun. The first people to use the solar calendar were probably the ancient Egyptians. Based on the flooding cycle of the Nile River, they set the year to 365 days, divided the year into 12 months of 30 days, and added 5 days of holidays after December to make up the calendar. It became 365 days. Later, Caesar, the ruler of the Romans, inserted these five days into different months. He also took two days out of February, which they considered unlucky, and inserted them into other months. In this way, the year There are seven 31-day months, four 30-day months, and one 28-day month. During the Roman period, astronomers already knew that a tropical year has 365.25 days. If we only follow this rule, there will be one day off every four years. So, they added the extra day to February. The calendar based on the changes in the moon phases is called the lunar calendar. Nowadays, not many countries use the lunar calendar. Only a few Arabs use the "Islamic calendar" which is compiled according to the lunar calendar method.

China’s lunisolar calendar

China’s lunisolar calendar is the third compilation method. It not only takes into account the moon’s waxing and waning changes, but also takes into account the annual apparent motion of the sun. . According to research, China has been using the lunisolar calendar since the Yin and Shang Dynasties.

An ordinary year of the lunisolar calendar has six 30-day months and six 29-day months, which add up to 354 days, which is 11 days different from the length of a year of 365 days. If it were always arranged like this, then there would be a difference of more than one month every three years. So the ancients came up with a way to add one month every three years. This extra month is called a leap month. However, people later found that three years plus one month was too few to make up for the 33 days left in the three-year gap; five years plus two leap months was too many, and it exceeded the five-year difference of 55 days. If we add 55 days in 19 years, Satisfactory results can be obtained with 7 leap months. The 19th return year is 6939.75 days. There are 228 months in 19 years plus 7 leap months, which is 235 months. The total number of 235 months is 6939.55 days, which is only 0.2 days different from the 6939.75 days in the 19 tropical years, which is less than 5 hours.

The lunisolar calendar can basically keep the months consistent with the climate. Unlike the lunar calendar, there may be snow even in June.

Twenty-four solar terms

The twenty-four solar terms refer to the Beginning of Spring, Rain, Waking of Insect, Vernal Equinox, Qingming, Grain Rain, Beginning of Summer, Xiaoman, Ear Grain, Summer Solstice, Minor Heat, Great Heat, Beginning of Autumn, Summer, White Dew, Autumnal Equinox, Cold Dew, Frost Descent, Beginning of Winter, Light Snow, Heavy Snow, Winter Solstice, Lesser Cold, and Big Cold. The odd numbers are called solar terms, and the even numbers are called Zhongqi. What is the significance of the twenty-four solar terms, and how are they included in the calendar?

The twenty-four solar terms actually divide the annual apparent motion of the sun into 24 equal parts. According to the ancient Chinese scale, the number of days in a week is 365.25 degrees, and each equal part is a little more than 15 degrees. For a long time, the ancient Chinese believed that the sun moved evenly, and if it moved one degree a day, each equal part would be equivalent to more than 15 days. The ancients determined the moment when the winter solstice occurred in a certain year based on actual observations, and then started to add up from this moment. If the winter solstice adds up to 15 days, it will get light snow, and if the light snow adds up to 15 days, it will get heavy snow, and so on to get the solar terms of the whole year.

Since the twenty-four solar terms completely describe the movement of the sun, it is closely connected with climate change; and the changes in phenology in nature and the time of farmers sowing in spring and autumn are directly determined by the climate. Therefore, the twenty-four solar terms are mostly named after phenological changes and the growth of crops. For example, "Jingzhe" refers to the sound of spring thunder, which disturbs small animals hibernating underground, and they will come out to move; "awnzhong" means the beginning of crops with awns. Ripe, this is also the time to start planting fall crops. Arranging the twenty-four solar terms is also an important part of the ancient Chinese calendar.

Knotting dates with knots and meeting each other with carved wood

Living in modern times, we can always know what month and day it is today. Because we have calendars everywhere on our walls, on our desks, on our watches, and on our computers. They are so commonplace in our lives that we have turned a blind eye to them.

But in ancient times, people did not have calendars to keep track of days. What should they do? When a person leaves home, how does he know how many days he has been away from home? In order to solve this problem, the ancients came up with a method of "knotting a rope to keep track of the day". When a person is about to go on a long journey, he ties a rope around his waist and ties a knot on the rope one day. After arriving at the destination, count the knots on the rope to know how many days he has been walking. When returning home, one knot will be untied after a day. When all the knots are untied, almost everyone will be home. This method was still used by some ethnic minorities in China even in the 1940s and 1950s.

If two people agree to meet again in ten days, they will carve ten notches on a small piece of wood or bamboo, then split it in the middle, each taking half, and every day, Both men shaved off a notch. When the ten carvings on the bamboo piece are finished, the day has come for them to meet again. This is the "meeting on carved wood."

Calendar in oracle bone tablets

Emperors and nobles in the Yin and Shang Dynasties often asked fortune tellers: How is the weather recently? How is the agricultural harvest this year? Is a solar or lunar eclipse that occurs on a certain day of a certain year a good or bad omen? The fortune teller would use a bronze knife to carve these questions on the tortoise shell, and then use a red-hot bronze stick to burn the inside of the tortoise shell. The hot bronze stick will crack the tortoise shell into different patterns, and the fortune teller will answer the questioner based on these patterns. These characters carved on tortoise shells became the oldest ancestor of our Chinese characters: oracle bone inscriptions.

On several pieces of oracle bones unearthed from the Yin Ruins in Anyang, Henan, a table of sixty stems and branches is neatly engraved. These oracle bone fragments do not have burn marks like others and are obviously not used for divination. Later generations speculate that they may have served as a calendar during the Yin and Shang Dynasties and were specially used to keep track of days. The method of recording the day with stems and branches is to use the ten heavenly stems: A, B, C, Ding, Wu, Ji, Geng, Xin, Ren, Gui and the twelve earthly branches: Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, and Hai match in turn, with sixty as a cycle. If a certain day is assumed to be Jiazi day, then the next day will be Yichou day, the third day will be Bingyin day, and so on, and so on. The method of keeping track of the stems and branches is an important creation of the ancient Chinese. Regarding the Yin Dynasty calendar, people generally believe that it uses the stems and branches to record the day, the moon's phase changes to record the month, and the sun's annual movement to record the year. There are twelve months in an ordinary year and 13 months in a leap year. The leap month added at the end of a year is called thirteen months. There are different sizes of moons. A big month has 30 days and a small month has 29 days. There are intervals between big and small months, and there are consecutive big months.

Astrology

Let us start with an astrology story to get a general understanding of how ancient Chinese astrologers performed horoscopes. During the Southern and Northern Dynasties, Cui Hao of the Northern Wei Dynasty was not only the emperor's imperial adviser, but also a famous astrologer who often participated in the decision-making of national affairs through astrology. Once, Tai Shi Ling reported to the emperor that the spark in the palace had lost its trace at some point and might have descended to a certain country to bring disaster to that country. The emperor was frightened after hearing this and immediately asked his minister where Mars had gone.

The Han 28 constellation disk unearthed in Fuyang, Anhui

Cui Hao judged based on the stems and branches of Mars missing for two days: namely "Gengwu" and "Xinwei", according to the twelve divisions Geng and Wu are both divisions of the Qin State, so Mars must have gone to Later Qin (a small country at the same time as the Northern Wei Dynasty). At that time, no minister in the court believed Cui Hao's words. As a result, eighty days later, Mars indeed appeared in Qin's dividing field, Jingsu, and stopped motionless in Jingsu. That year, a severe drought occurred in the Later Qin Kingdom. Rumors spread and people's hearts fluctuated. The next year the king died, his two sons fought with each other, and within a few years the country fell. This horoscope was called divine divination by the people at the time. In fact, Cui Hao knew that Mars moved forward, retrograde, and stayed in motion. With a little calculation, he could know where Mars went; and as the emperor's minister, Consultant, he has mastered a lot of the social and political situation of the Post Qin Dynasty, so there is nothing mysterious about his judgment on the fate of the Post Qin country.

Division

During the Spring and Autumn Period and the Warring States Period, there were countless feudal vassal states. This raises a question for astrologers: the world is so big, and there are so many feudal vassal states, but there is only one sky. If a certain celestial phenomenon occurs in the sky, which country and which country should be warned? What about region? The solution of the ancient Chinese was to let the states and countries on the earth divide the celestial sphere. In this way, the celestial phenomena that appeared in a certain celestial region would correspond to a certain state or country. This is the theory of division.

"Book of Jin Astronomical Records" records a list of twelve states including Yanzhou, Yuzhou, Youzhou, Yangzhou, Qingzhou, Bingzhou, Xuzhou, Jizhou, Yizhou, Yongzhou, Sanhe and Jingzhou, Zheng and Song Dynasties Complete information on the twelve ancient kingdoms of Yan, Wu, Yue, Qi, Wei, Lu, Zhao, Wei, Qin, Zhou, and Chu that were divided into twelve times, twelve Chens, and twenty-eight constellations. As for the twenty-eight constellations, since twenty-eight is not an integer multiple of twelve, and the scope of the twenty-eight constellations in the sky may be wide or narrow, astrologers divide certain constellations into different states and princes. country.

Judging from the names of the divisions of the twelve kingdoms recorded in "Book of Jin Tianwen Zhi", the theory of divisions as the basis of astrology may have been finalized in the Spring and Autumn Period and the Warring States Period, but as early as in "Li of Zhou" There is a sentence: "The land of Kyushu is distinguished by the stars and soil, and all the enclosed areas are divided into stars to observe the evil spirits and auspiciousness." This almost touches on all the key points of the theory of division.

Sui star chronology

The Sui star is Jupiter, and its revolution period is 11.86 years. According to the ancients, Jupiter would appear in the same area of ??the sky again about twelve years later. Therefore, people evenly divided the equatorial zone into twelve equal parts, which were called Xingji, Xuanzhuo, Juanzi, Jianglou, Daliang, Shichen, Quailshou, Quailhuo, Quailwei, and so on from west to east starting from the winter solstice. Birthday star, fire, split wood. This division method is called "twelve times". When some major historical event occurred, noting the position of Jupiter during the twelve times told the time of the event.

For example, "Guoyu" records the time when King Wu of Zhou defeated King Zhou of Yin and said: "King Wu defeated Zhou, and he was in the quail fire." This chronology is called the Suixing chronology.

The Twelve Times of the Twelve Centuries

Yellow-Red Crossing Angle

The earth revolves and rotates. The great circle formed by its orbit extending outward and intersecting the celestial sphere is called The ecliptic; the great circle formed by the outward extension of the rotational orbit and the intersection with the celestial sphere is called the equator. The ecliptic plane and the equatorial plane do not coincide. There is an angle of about 24 degrees between them, which is called the ecliptic angle. In ancient China, it was called the ecliptic distance.

The armillary sphere was the main instrument used in ancient China to measure the positions of the sun, moon and five stars. The data it measured were the equatorial coordinates of celestial bodies; and we all know that the sun moves on the ecliptic, as do the other moons and the five planets. It moves near the ecliptic, so when the ancients compiled calendars, they often converted equatorial coordinates into ecliptic coordinates. To do such a conversion, it is inevitable to use the data of yellow and red angles. People in the Han Dynasty generally believed that the intersection angle between yellow and red was about 1 minute. Xu Ang in the Tang Dynasty measured the error to be 37 seconds, achieving a very high accuracy.

The "Zhou Bi Suan Jing" records a very simple method of measuring the Huangchi distance using the eight-foot gui table. The shadow length of the table measured at noon on the winter solstice is one foot and three feet, and the shadow length of the summer solstice is one foot and five inches. Knowing the geographical latitude of the measurement, we can use the most basic astronomical knowledge and trigonometry knowledge to find the Huangchi Distance.

Precession

Precession is caused by the attraction of the sun, moon and planets to the protruding part of the earth's equator, causing the direction of the earth's rotation axis to change. Many people have played with a small toy called a top when they were young. The earth, with its axis of rotation constantly changing, is like a large tilt-rotating top. It rotates around its axis, and at the same time, the axis of rotation is also spinning in circles in the sky, but the speed is not It's just as fast as a toy top. It takes one day for the Earth to rotate once, but it takes about 26,000 years for its axis to rotate once in the sky. This slow movement is the precession of equinox. Precession manifests itself in two aspects in astronomical observations: first, the intersection of the ecliptic and the equator: the vernal and autumnal equinoxes move westward along the ecliptic; first, the north celestial pole constantly changes position in the background of stars.

Chart of the causes of precession

The vernal equinox moves westward

In 330 AD, Yu Xi of the Eastern Jin Dynasty observed the moment when a certain star passed south of the sky at dusk. When comparing with ancient records, he found that the spring and autumn equinoxes and the winter and summer solstice points had moved westward. Therefore, he came to a very important understanding: the sun orbits a certain position in the background of stars and then returns to its original position. The time it takes to reach a location is not equal to the time interval from one winter solstice to the next. Therefore, he put forward the view that "the sky itself is the sky, and the years are themselves the years." This is the concept of precession. At the same time, he also gave the information that the winter solstice point moves one degree westward along the equator every fifty years, which became an ancient Chinese comparison. The beginning of increasingly accurate determination of precession values.

On several pieces of oracle bones unearthed from the Yin Ruins in Anyang, Henan, a table of sixty stems and branches is neatly engraved. These oracle bone fragments do not have burn marks like others and are obviously not used for divination. Later generations speculate that they may have served as a calendar during the Yin and Shang Dynasties and were specially used to keep track of days. The method of recording the day with stems and branches is to use the ten heavenly stems: A, B, C, Ding, Wu, Ji, Geng, Xin, Ren, Gui and the twelve earthly branches: Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu and Hai match in turn, with sixty as a cycle. If a certain day is assumed to be Jiazi day, then the next day will be Yichou day, the third day will be Bingyin day, and so on, and so on. The method of keeping track of the stems and branches is an important creation of the ancient Chinese. Regarding the Yin Dynasty calendar, people generally believe that it uses the stems and branches to record the day, the moon's phase changes to record the month, and the sun's annual movement to record the year. There are twelve months in an ordinary year and 13 months in a leap year. The leap month added at the end of a year is called thirteen months. There are different sizes of moons. A big month has 30 days and a small month has 29 days. There are intervals between big and small months, and there are consecutive big months.

Astrology

Let us start with an astrology story to get a general understanding of how ancient Chinese astrologers performed horoscopes. During the Southern and Northern Dynasties, Cui Hao of the Northern Wei Dynasty was not only the emperor's imperial adviser, but also a famous astrologer who often participated in the decision-making of national affairs through astrology. Once, Tai Shi Ling reported to the emperor that the spark in the palace had lost its trace at some point and might have descended to a certain country to bring disaster to that country. The emperor was frightened after hearing this and immediately asked his minister where Mars had gone.

The Han 28 constellation disk unearthed in Fuyang, Anhui

Cui Hao judged based on the stems and branches of Mars missing for two days: namely "Gengwu" and "Xinwei", according to the twelve divisions Geng and Wu are both divisions of the Qin State, so Mars must have gone to Later Qin (a small country at the same time as the Northern Wei Dynasty). At that time, no minister in the court believed Cui Hao's words. As a result, eighty days later, Mars indeed appeared in Qin's dividing field, Jingsu, and stopped motionless in Jingsu. That year, a severe drought occurred in the Later Qin Kingdom. Rumors spread and people's hearts fluctuated. The next year the king died, his two sons fought with each other, and within a few years the country fell. This horoscope was called divine divination by the people at the time. In fact, Cui Hao knew that Mars moved forward, retrograde, and stayed in motion. With a little calculation, he could know where Mars went; and as the emperor's minister, Consultant, he has mastered a lot of the social and political situation of the Post Qin Dynasty, so there is nothing mysterious about his judgment on the fate of the Post Qin country.

Division

During the Spring and Autumn Period and the Warring States Period, there were countless feudal vassal states. This raises a question for astrologers: the world is so big, and there are so many feudal vassal states, but there is only one sky. If a certain celestial phenomenon occurs in the sky, which country and which country should be warned? What about region? The solution of the ancient Chinese was to let the states and countries on the earth divide the celestial sphere. In this way, the celestial phenomena that appeared in a certain celestial region would correspond to a certain state or country. This is the theory of division.

"Book of Jin? Astronomical Chronicles" records a list of the twelve states of Yanzhou, Yuzhou, Youzhou, Yangzhou, Qingzhou, Bingzhou, Xuzhou, Jizhou, Yizhou, Yongzhou, Sanhe and Jingzhou, Zheng and Song Dynasties Complete information on the twelve ancient kingdoms of Yan, Wu, Yue, Qi, Wei, Lu, Zhao, Wei, Qin, Zhou, and Chu that were divided into twelve times, twelve Chens, and twenty-eight constellations. As for the twenty-eight constellations, since twenty-eight is not an integer multiple of twelve, and the scope of the twenty-eight constellations in the sky may be wide or narrow, astrologers divide certain constellations into different states and princes. country.

Judging from the names of the twelve kingdoms recorded in the "Book of Jin? Astronomical Records", the theory of division as the basis of astrology may have been finalized in the Spring and Autumn Period and the Warring States Period, but as early as in "The Rites of Zhou" There is a sentence: "The land of Kyushu is distinguished by the stars and soil, and all the enclosed areas are divided into stars to observe the evil spirits and auspiciousness." This almost touches on all the key points of the theory of division.

Sui star chronology

The Sui star is Jupiter, and its revolution period is 11.86 years. According to the ancients, Jupiter would appear in the same area of ??the sky again about twelve years later. Therefore, people evenly divided the equatorial zone into twelve equal parts, which were called Xingji, Xuanzhuo, Juanzi, Jianglou, Daliang, Shichen, Quailshou, Quailhuo, Quailwei, and so on from west to east starting from the winter solstice. Birthday star, fire, split wood. This division method is called "twelve times". When some major historical event occurred, noting the position of Jupiter in twelve times told the time of the event. For example, "Guoyu" records the time when King Wu of Zhou defeated King Zhou of Yin and said: "King Wu defeated Zhou, and he lived in Quail Fire." This chronology is called the Suixing chronology.

The Twelve Times of the Twelve Centuries

Yellow-Red Crossing Angle

The earth revolves and rotates. The great circle formed by its orbit extending outward and intersecting the celestial sphere is called The ecliptic; the great circle formed by the outward extension of the rotational orbit and the intersection with the celestial sphere is called the equator. The ecliptic plane and the equatorial plane do not coincide. There is an angle of about 24 degrees between them, which is called the ecliptic angle. In ancient China, it was called the ecliptic distance.

The armillary sphere was the main instrument used in ancient China to measure the positions of the sun, moon and five stars. The data it measured were the equatorial coordinates of celestial bodies; and we all know that the sun moves on the ecliptic, as do the other moons and the five planets. It moves near the ecliptic, so when the ancients compiled calendars, they often converted equatorial coordinates into ecliptic coordinates. To do such a conversion, it is inevitable to use the data of yellow and red angles. People in the Han Dynasty generally believed that the intersection angle between yellow and red was about 1 minute. Xu Ang in the Tang Dynasty measured the error to be 37 seconds, achieving a very high accuracy.

The "Zhou Bi Suan Jing" records a very simple method of measuring the Huangchi distance using the eight-foot gui table. The shadow length of the table measured at noon on the winter solstice is one foot and three feet, and the shadow length of the summer solstice is one foot and five inches. Knowing the geographical latitude of the measurement, we can use the most basic astronomical knowledge and trigonometry knowledge to find the Huangchi Distance.

Precession

Precession is caused by the attraction of the sun, moon and planets to the protruding part of the earth's equator, causing the direction of the earth's rotation axis to change. Many people have played with a small toy called a top when they were young. The earth, whose axis of rotation is constantly changing, is like a large tilt-rotating top. It rotates around its axis, and at the same time, the axis of rotation also rotates in circles in the sky, but the speed is not It's just as fast as a toy top. It takes one day for the Earth to rotate once, but it takes about 26,000 years for its axis to rotate once in the sky. This slow movement is the precession of equinox. Precession manifests itself in two aspects in astronomical observations: first, the intersection of the ecliptic and the equator: the vernal and autumnal equinoxes move westward along the ecliptic; first, the north celestial pole constantly changes position in the background of stars.

Chart of the cause of precession

The vernal equinox moves westward

In 330 AD, Yu Xi of the Eastern Jin Dynasty observed the moment when a certain star passed south of the sky at dusk. When comparing with ancient records, he found that the spring and autumn equinoxes and winter and summer solstice points had all moved westward. Therefore, he came to a very important understanding: the sun orbits a certain position in the background of stars and then returns to its original position. The time it takes to reach a location is not equal to the time interval from one winter solstice to the next. Therefore, he put forward the view that "the sky is the sky, and the years are the years." This is the concept of precession. At the same time, he also gave the information that the winter solstice point moves one degree westward along the equator every fifty years, which became an ancient Chinese comparison. The beginning of increasingly accurate determination of precession values.