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What is the lunar calendar?

What is the lunar calendar?

Lunar calendar (the lunar calendar in China) takes the time of the first month of the lunar calendar as the average time of the calendar month.

This is the same as the pure lunar calendar, but the lunar calendar adopts the method of setting leap months and 24 solar terms, so that the average length of the calendar year is equal to the tropic year, which has the elements of the solar calendar, so it is better than the pure lunar calendar. It is said that our ancestors used this calendar in all lunar calendars as early as the Xia Dynasty (before17th century BC).

So people also call it the summer calendar. After liberation, it was still called the summer calendar. After 1970, it was renamed as the "Lunar Calendar" in China.

As for the origin of the name "lunar calendar", it is probably because the country has been founded on agriculture since ancient times, so the calendar must serve agriculture. The lunar calendar is based on the new moon.

The time of the first lunar month is 29th 12 hours, 44 minutes and 3 seconds (that is, 29.5366 days), so the lunar calendar is also 30 days for the big month and 29 days for the small month, but it is not exactly the same as the pure lunar calendar, because the pure lunar calendar is arranged alternately with big and small months, and the size and month of the lunar calendar are determined by calculation. The first day of each month in the lunar calendar happens to be a "new moon" (that is, the moon is in the middle of the sun and the earth faces the earth with half of the darkness).

Sometimes there may be two big months or two small months in a row. Because the first month of the lunar calendar is slightly longer than 29 and a half days, there are about 53 big months and 47 small months in every 100 calendar month of the lunar calendar.

The lunar calendar basically takes1February as a year, but the time of 12 lunar month is 354.3667 days, which is about 1 1 day different from the tropical year. This will add 33 days every three years, that is, an extra month.

In order to eliminate the extra days, one month is added every three years, which is the leap month of the lunar calendar. A year with a leap month is also called a leap year.

Therefore, the lunar leap year has 13 months. As for the leap month, it is determined by the solar terms.

Lunar calendar is one of the representatives of traditional culture in China. Its accuracy, cleverness and humor condense the wisdom of the Chinese nation. According to China's historical records, from the era of the Yellow Emperor to the end of the Qing Dynasty, Yi * * used 102 calendar methods, which basically belonged to the nature of yin and yang calendars.

This shows that the people of China reconciled the pure lunar calendar with the solar calendar three or four thousand years ago. This calendar, which takes into account the length of the first month of the lunar calendar and the return year, is also a great creation of our Chinese ancestors.

The lunar calendar has been used for a long time in China, also known as the summer calendar. It was once dismissed as an "abandoned calendar".

The last revision was made in the seventh year of Qing Dynasty (about 1742), which was determined by the revision of Tang Ruowang's Constitutional Calendar by Zai Jinxian. Farmers in China are very familiar with the lunar calendar, and many folk festivals are based on the lunar calendar.

The twenty-four solar terms, the new moon, the moon, the zodiac and so on are widely circulated in the lunar calendar. The lunar calendar is less 1 1 day than the solar calendar every year, and it is 33 days less than three years. Therefore, every three years plus one month is called leap month.

But there are still three or four days left in the leap of three years, which is still inaccurate. So the method of two jumps in five years was adopted.

But in five years, I made two leaps and added four or five days. So it took eight years and three leaps to remedy it, but two days were missing in eight years and three jumps.

After repeated astronomical observations and practical tests, the seven-leap method of 19 is finally worked out, that is, seven leap months are set between 19. Gregorian calendar 19 is 6939.60 18 days, and lunar calendar 19 (including 7 leap months) is 6939.65438+0 days, so the difference between the two calendars is only about 2 hours, which can be said to be more accurate.

It should also be pointed out that Zu Chongzhi, an ancient Chinese scientist, creatively put forward the leap method of setting 39 1 year 144 leap month, which is more accurate. It can be seen that the lunar year is sometimes twelve months and sometimes thirteen months, which is not chaotic, but has strict scientific laws.

However, which month of the year is a leap month? There are different ways to deal with the position of the lunar leap month in history. Generally speaking, before the early Western Han Dynasty, the leap month was placed at the end of the year.

For example, in the early Han Dynasty, September was regarded as the last month of the year, and the leap month at that time was placed after September, which was called "post-September". Later, with the gradual refinement of the calendar, the arrangement method of leap months also has a new regulation, that is, the month without neutral gas is regarded as a leap month.

This leap rule is still in use today. So here is a special introduction to China Automobile.

The length of the calendar month in the lunar calendar is based on the first month of the lunar calendar. 30 days in the first lunar month and 29 days in the second lunar month. The first lunar month and the second lunar month complement each other, making the average length of calendar months close to the first lunar month. Lunar New Moon is the first day of the month-the first day of the month.

Astronomically speaking, the so-called "new moon" has a definite moment, that is, the ecliptic of the moon is the same as that of the sun. The basis of the name of the month in the lunar calendar is determined by "Zhongqi".

That is, the month containing "rain" is January; February is a month with "vernal equinox"; March is the month of Grain Rain; April is a month with "small fullness"; May is the month of "summer solstice"; June is the month of "great summer heat"; July is the month of "summer heat"; August is the month of autumnal equinox; September is the month of "first frost"; 10 is the month of "light snow"; 1 1 month is the month of "winter solstice"; 1February is the month of heavy snow. As a leap month of last month, the length of the calendar year depends on the tropic year, but the days of tropic year are more than 12 months and shorter than 13 months. When ancient astronomers compiled the lunar calendar, it was important to make every day in a month contain the meaning of the moon phase, that is, the first day was moonless night and the fifteenth day was full moon. There are seven leap years and each leap year has thirteen months.

Why adopt the method of "seven leaps in nineteen years"? The average lunar month is 29.5306 days, and there are 12.368 lunar months in a tropical year. The progressive scores of the fractional part of 0.368 are 1/2, 1/3, 3/8, 4/1,7/68. Because 19 tropical year = 6939. 18 days, and 19 lunar year (after seven leap months) * * has 235 moons, which is equal to 6939.438+00 days, so the two are almost the same.

The insertion of the lunar leap month has been completely artificial since ancient times.

What is the lunar calendar and what is the solar calendar?

Lunar calendar, solar calendar and yin-yang calendar are always inseparable from time and space in human life and production. How can we remember, express clearly to others, and even accurately record an event and a phenomenon? There must be a fixed method, that is, the problem of Gregorian year, Gregorian month, Gregorian day and Gregorian time.

It is easy to observe a day consisting of sunrise, sunset and day-night cycle. The longer the moon, the longer the month and the longer the year. After long-term observation, it is found that the full period and short period of the moon (the first month of the lunar calendar) are about 30 or 29 days, and the seasonal period (the tropic year) is about 365 or 366 days.

If we don't follow these standards, but take the orientation of the sun and the moon in the stellar background of the celestial sphere as the standard, then in astronomy, there are also sidereal months (shorter than the moon) and sidereal years (slightly older than the regression). Others include the near-point month and the intersection month, so I won't talk about it here.

Year, month and day are endless cycles. Originally, there was no beginning or end, but for convenience, people always designated a beginning. Different nationalities, different regions and different times have different regulations, so the problem of mutual conversion between the beginning of the year and the beginning of the month arises.

There are several ways to calculate the beginning of a day, such as dawn, pingdan, sunset and midnight. There are several ways to calculate the beginning of a month, such as starting from the full moon and starting from the appearance of the new moon.

At the beginning of a year, there are many calculation methods, such as winter solstice, vernal equinox, and other signs. The most troublesome problem is that a new moon is not exactly thirty days, but a little over twenty-nine and a half days.

But in real life, we can't divide a day into two halves, so that the upper part belongs to last month and the lower part of the same day belongs to the next month. That's too inconvenient. If 365 days of a year are defined as 12 months ***354 days, there is still 1 1 day left. There is no common multiple between 29.5309 days of the moon and 365.2422 days of the Tropic of Cancer, so a cycle cannot be formed. What do we do? It is precisely because of the different ways to deal with these problems that various calendars have appeared in the world.

To sum up, there are only three kinds: lunar calendar, solar calendar and combined calendar of yin and yang. The first two only care about one end, and the third is to take care of both ends.

Let's talk about the lunar calendar first. Simply put, it is based on the cycle of the moon. The so-called "simplicity" means only caring about the moon, regardless of seasonal changes such as climate change caused by the relationship between the sun and the earth.

The moon is also called "lunar calendar", so this calendar is called "lunar calendar" for short. When the moon and the sun are just on both sides of the earth, the soft moonlight shines on the sleeping earth all night. The most round moment of the moon is called "full moon", also called "looking".

Because the moon is always in motion; So strictly speaking, the real "lookout" is only a very short moment. For an instant, ordinary people can't observe such subtle changes. Usually, the whole day including the real "lookout" is called "lookout day", or simply "lookout", which is one of the most easily observed and remarkable astronomical phenomena. On the contrary, when the moon is between the sun and the earth, people can't see any images of the moon at all. This day is called "New Moon". Astronomy refers to the moment when the longitude of the ecliptic of the moon coincides with the longitude of the ecliptic of the sun.

Astronomers call the period of moon phase change, that is, the length of time from new moon to new moon or from looking to looking, "Shuowangyue", and the Tibetan calendar is called tshes-zla, which can also be translated as "lunar month". Many years' observation shows that the length of Wang Shuo's moon is not fixed, and its average length is 29 days 12 hours and 44 minutes, that is, 29.5306 days, which is very important data for making calendars and must be firmly remembered.

It can be roughly recorded as 29 and a half days. The most typical lunar calendar is the "monthly calendar" in the * * * calendar (different from the "palace calendar" used in agriculture), which was called "* * * calendar" in ancient China.

It always takes 12 lunar months as a year, with an average of 29.5 days per month, and 12 ***354 days. At the end of leap year, 355 days plus 10 days, and there is no leap month. In addition, we know that human life and production, especially in temperate regions of the earth, are closely related to the climate change of warm spring, hot summer, cool autumn and cold winter.

This year consists of four seasons: spring, summer, autumn and winter. It is called "tropic year", that is, the cycle of the sun from the highest to the lowest, and then from the lowest to the highest. Its strict definition in astronomy is: "the time interval between two consecutive passes through vernal equinox on weekdays."

According to the results of long-term astronomical observation, it is known that the length of the tropic of cancer is 365.2422 days a year, that is, 365 days, 5 hours, 48 minutes and 46 seconds, which is another very important data when making calendars. It must be firmly remembered that it can be roughly recorded as 365 days 1/4 days. The data obtained by ancient calendar mathematicians did not reach such accuracy at once, but gradually approached the accuracy with the development of calendar.

It can be seen that there is a difference of eleven days between the tropic year and the lunar year (that is, the lunar year taught by * * * *), and it will accumulate to 180 days after sixteen or seventeen years, which means that winter and summer will be reversed. There is no leap month in the pure lunar calendar, but there are leap months in both Tibetan and lunar calendars, although the average year is 354 or 355 days, and the year with leap months is 384 days. Therefore, it cannot be said that the lunar calendar is a lunar calendar, and the Tibetan calendar is not a lunar calendar, but a yin-yang calendar.

2. Summer Calendar, Lunar Calendar and Old Calendar Let's talk about the origin of the name "Summer Calendar". As early as 2400 or 500 years ago, Han people began to calculate the twelve earthly branches (Zi, Ugly, Yin, Mao, ...), with the month of winter solstice as the next month, followed by ugly month, silvery month and the month before winter solstice as the sea month.

Taking February as the first month of the year is called "Jianzi", and so on. According to some historical records, the Xia Dynasty built the Yin Dynasty, the Shang Dynasty built the ugliness, the Zhou Dynasty built the Zi Dynasty, and the Qin Dynasty built the sea.

The sea was still built in the early Han Dynasty, and it was rebuilt in the first year of Emperor Wu of Han Dynasty (A.D. 104). Since then, although the calendar has changed many times, Yin Jian has never changed (except for a few short years when Wu Zetian adopted Zhou Zheng).

Judging from the adoption of Yin Jian, the Han Dynasty adopted taichu calendar.

What does the lunar calendar mean?

At present, there are two calendars used in China: Gregorian calendar (also called solar calendar) and Lunar calendar (also called lunar calendar). The Gregorian calendar is 365 days, which is 0.2422 days shorter than the tropic year, so it is called a normal year. In this way, the difference of four years is 23 hours 15 minutes and 4 seconds (5 hours, 48 minutes and 46 seconds *4), which is close to one day. Every 400 years will add 3 days, 2 hours, 53 minutes and 20 seconds (44 minutes and 56 seconds * 100), so there should be 3 days less every 400 years. In order to facilitate the calculation, the rule of "leap every four years, not leap in a hundred years, and leap again in a hundred years" was formulated. At present, there are Gregorian calendar (also called solar calendar) and lunar calendar (also called lunar calendar), sometimes it is 13 months, but one of 13 months is called leap month, such as leap July and March. , not included in the normal month series, because 12 lunar month is 354.3672 days (29.5306* 12), which is 60% different from the tropic year. So after three years, a leap month will be added to eliminate this error, so there will be 13 months in this year. In the Northern and Southern Dynasties, astronomer Zu Chongzhi found that if seven leap months were inserted in 19, it was almost equal to 19 tropic year. This is the seventh leap of 19. This discovery predates the ancient Greeks 160 years. The solar calendar is based on the revolution of the earth around the sun, and the lunar calendar is based on the full period and short period of the moon. These two calendars are called Yin and Yang calendars ZYL/2004/2004 10965438+.

Llyyqqchh.blogdriver/llyyqqchh/115624 reference:

zhidao.baidu/question/3449203? MD = 3 .

What is the lunar calendar? What is the lunar calendar? What is the solar calendar?

At present, there are two calendars used in China: Gregorian calendar (also called solar calendar) and Lunar calendar (also called lunar calendar). The Gregorian calendar is 365 days, which is 0.2422 days shorter than the tropic year, so it is called a normal year. In this way, the difference of four years is 23 hours 15 minutes and 4 seconds (5 hours, 48 minutes and 46 seconds *4), which is close to one day. Add 3 days, 2 hours, 53 minutes and 20 seconds (44 minutes and 56 seconds * 100) every 400 years, so add 3 days every 400 years. In order to facilitate the calculation, the rule of "leap every four years, not leap in a hundred years, and leap again in a hundred years" was formulated.

At present, there are Gregorian calendar (also called solar calendar) and lunar calendar (also called lunar calendar) in use in China. According to the needs of agricultural production, the lunar calendar is adopted. The lunar calendar is sometimes1February and sometimes1March, but one month in1March is called leap month, such as leap July and leap March. It is not included in the normal month series. Because the moon 12 is 354.3672 days (29.5306* 12), which is 1 1 day different from the tropical year, there will be 30 days more after three years, so a leap month will be added after three years to eliminate this error. If seven leap months are inserted into 19, it is almost equal to 19 tropical year, that is, 19 leap months. This discovery predates the ancient Greeks 160 years.

The solar calendar is based on the revolution of the earth around the sun, the lunar calendar is based on the moon, and the yin-yang calendar is based on both.

What is the lunar calendar and what is the solar calendar?

The lunar calendar in astronomy mainly refers to the calendar arranged according to the moon phase cycle. The calendar of the moon's one-week orbit around the earth (taking the sun as the reference object, the actual moon's orbit is more than one week) is January, that is, the first month of the lunar calendar is used as the basis for determining the calendar month, and a year is twelve calendar months. In agrometeorology, the lunar calendar is commonly known as lunar calendar, lunar calendar, ancient calendar and old calendar, which refers to the traditional summer calendar in China. Astronomically speaking, the summer calendar is actually a kind of lunar calendar.

Calendar based on the apparent movement of the sun, referred to as "solar calendar" or "solar calendar"; The moon is "lunar calendar", and the calendar made according to the apparent motion law of the moon is called "lunar calendar" for short.

What is the lunar calendar and what is the solar calendar?

The lunar calendar uses the period of the moon to determine the month. The moon never grows up slowly, becomes a full moon, that is, a round moon, then becomes smaller and finally disappears. It's called a month at this time. So it is also called a calendar. The ancient moon in China was also called the lunar calendar, so the monthly calendar was called the lunar calendar. The moon revolves around the earth for about twenty-nine and a half days. So a month in the lunar calendar is 29 or 30 days. A year is called 12 months, and a year is 354 or 355 days. However, it takes about 365 and a quarter days for the earth to go around the sun. One year after the lunar calendar, the earth has not returned to the starting point of the orbit, about ten days short. In this way, one month is missing in three years, and 18 is missing for half a year. That is to say, after 18, the first day of the first month will be in summer instead of winter. What should I do? Astronomers in ancient China figured out how to add one month every three years. The usual year is twelve months, and a year with one month is called leap year, which is thirteen months. Although this can ensure that the first day of the first month is winter, the position of the earth on the orbit of revolution on the first day of the first month of the lunar calendar is not fixed, so the position of the earth on the orbit of revolution on other days is not fixed, about ten days apart every three years. This is why according to the solar calendar, the Spring Festival is sometimes in January and sometimes in February.

There is also a name in the lunar calendar. But farmers can't farm according to the lunar calendar, because the days in the old calendar are not fixed. If the date of farming is mistaken for several tens of days, the harvest will be greatly affected. In order to solve this problem, ancient astronomers in China came up with a good way to divide the earth's orbit into 24 parts. That is, China's 24 solar terms. Farmers use these 24 solar terms to farm, not the lunar calendar.

The solar calendar, also known as the solar calendar, uses the period of the earth's revolution around the sun to make a year have 365 days, and then divides it into 12 months. Similar to the lunar calendar, the position of the days in the solar calendar on the orbit of revolution is also changing, with a difference of one day every four years, which is added to February. In this way, the swing of the solar calendar day is very small, only one or two days. For people, this day or two is nothing and can be completely ignored. So the solar calendar doesn't need solar terms.

What is the lunar calendar? What is the solar calendar?

The solar calendar is different from the lunar calendar. At present, there are two calendars used in China: solar calendar (also called solar calendar) and lunar calendar (also called yin-yang calendar). The Gregorian calendar defines a year as 365 days, which is 0.2422 days shorter than the tropical year, and it is called a normal year. So the difference of four years is 23 hours 15 minutes and 4 seconds (5 hours, 48 minutes and 46 seconds *4), which is close to 1. Add 44 minutes and 56 seconds every four years and 3 days, 2 hours, 53 minutes and 20 seconds every 400 years (44 minutes and 56 seconds * 100). So we have to add three days every 400 years. In order to facilitate the calculation, the rule of "leap every four years, not leap in a hundred years, and leap again in a hundred years" was formulated.

At present, there are Gregorian calendar (also called solar calendar) and lunar calendar (also called lunar calendar) in use in China. According to the needs of agricultural production, the lunar calendar is adopted. The lunar calendar is sometimes1February and sometimes1March, but one month in1March is called leap month, such as leap July and leap March. It is not included in the normal month series. Because the moon 12 is 354.3672 days (29.5306* 12), which is 1 1 day different from the tropical year, there will be 30 days more after three years, so a leap month will be added after three years to eliminate this error. If seven leap months are inserted into 19, it is almost equal to 19 tropical year, that is, 19 leap months. This discovery predates the ancient Greeks 160 years.

The solar calendar is based on the revolution of the earth around the sun, the lunar calendar is based on the moon, and the yin-yang calendar is based on both.

What does the lunar calendar mean?

The full name of the lunar calendar is the lunar calendar or the pure lunar calendar.

The lunar calendar is based on the cycle of the moon, which is the new moon. Because the ancients called the moon "lunar calendar", it was called "lunar calendar" for short. It is difficult to determine the exact date of the lunar calendar, but judging from the Oracle bones in Oracle Bone Inscriptions, the lunar calendar was quite popular in the Yin Dynasty.

The main feature of the lunar calendar is that the length of the calendar month is determined according to the astronomical phenomena, that is, the phase of the moon, and the average length of the calendar month is roughly the same as that of Wang Shuoyue. 5306 days, etc.

The length of a year is only an integer multiple of a calendar month, which has nothing to do with the tropical year. Therefore, the month of the lunar calendar has nothing to do with the four seasons.

The date of the lunar calendar indicates a certain moon phase, that is, the first day is the new moon, that is, the new moon; The fifteenth, sixteenth or seventeenth is the full moon, which means hope; The seventh and eighth days are the first quarter moon; Twenty-two and twenty-three are the last quarter moons, and it is very convenient for the ancients to judge the date by the phase of the moon. The change of the moon phase is the easiest astronomical phenomenon to see, so most of the calendars in various countries have the lunar calendar first and then the solar calendar.

However, because the lunar calendar has nothing to do with the tropical year, it is not harmonious with agricultural production and people's daily life, and it was gradually eliminated. Nowadays, except for a few countries that still use a lunar calendar called "hijri" for religious reasons, all other countries have given up.

In addition,. 19 12 after China adopted the Gregorian calendar to arrange the months, people called it the Gregorian calendar, while the traditional summer calendar coexisting with the people was popularly called the lunar calendar.

1. The origin of the Gregorian calendar is the Gregorian calendar as well. It is international. Since the first year of the Republic of China, China has adopted the solar calendar, which is symmetrical with the old calendar of China. The solar calendar is also called the "new calendar".

The solar calendar takes one year for the earth to make a circle around the sun. ***365 days, 5 hours, 48 minutes and 46 minutes.

An average year is only an integer of 365 days, not a mantissa. The solar calendar is divided into 12 months, 3 1 day for the big month, 30 days for the small month, and only 28 days in February.

It is also stipulated that before July, a single month is a big month and a double month is a small month; After August, two months are big months and one month is small months. The remaining 5 hours, 48 minutes and 46 seconds each year, there is only one day in about four years, and this day is added in February of the fourth year. This year is called leap year, so February in leap year has 29 days.

2. Determination of leap years in the solar calendar Generally speaking, if the year of the solar calendar is divided by 4, leap years can be divided, such as 1984, 1988. However, because the exact number of days in a solar calendar year should be 365 days, 5 hours, 48 minutes and 46 seconds, 5 hours, 48 minutes and 46 seconds more than the normal year and 23 hours 15 minutes and 4 seconds more than the four-year calendar.

If one day is added every four years, it will add 44 points and 56 points, and almost three days in 400 years, then three days will be deducted every 400 years. Therefore, a supplementary provision is made: every solar year is a full hundred years, such as 1800,1900,2000, etc. , divisible by 400, so it is not a leap year.

But 2000 is a leap year, because its February has 29 days. 3, the origin of the lunar calendar The lunar calendar takes the full moon of the moon as a month, ***29 days and a half.

For the convenience of calculation, the big moon is customized for 30 days and the small moon is customized for 29 days. During the period of 65438+mid-February of a year, generally, large and small months are arranged alternately. There are about 365 days in the lunar calendar year, and there is no difference between a normal year and a leap year.

The lunar calendar does not consider the movement of the earth around the sun, so the changes of the four seasons in the lunar calendar have no fixed time and cannot reflect the seasons, which is a great shortcoming. In order to overcome this shortcoming, people later decided on a new calendar, which is the so-called yin-yang desk calendar.

The summer calendar (also called lunar calendar or lunar calendar) still in use in China is this kind of lunar calendar. Like the lunar calendar, it customizes a month according to the time when the moon wanes, that is, 30 days in the big month and 29 days in the small month, but it also adopts the method of adding leap months to make the average number of days in a year close to that in the solar calendar to adjust the four seasons.

The lunar calendar has a leap month every two or three years. 4, the determination of the lunar calendar leap month As for which month of the lunar calendar, this involves the solar terms.

There are 24 solar terms in a year, which is just a traditional saying. In detail, it should be said that there are twelve solar terms and twelve neutral terms in a year. Which of the twelve qi belongs to which month is regular: rain is the qi of the first month; The vernal equinox is in mid-February; Grain Rain is the spirit of March; Xiaoman is the spirit of April; The solstice in summer is mid-air in May; The summer heat is in mid-June; Summer heat is the qi of July; The autumnal equinox is in mid-August; The first frost is the breath of September; Light snow is the neutral atmosphere in October; The winter solstice is 1 1 mid-month; It's freezing in mid-air in December.

As for which month the ten solar terms are in, that is not necessarily the case. A month in the lunar calendar averages a little more than 29 and a half days, but the average interval from one breath to the next is less than 30 and a half days.

In this way, the monthly air in the lunar month will be delayed by 1 day. At a certain time, qi is not in the middle of the month but moved to the end of the month. If next month is a miscarriage, there will probably be no gas in this month, because the gas will be moved to the beginning of the third month. The middle month is not neutral, even if last month was a leap month.

Take 1998 as an example: June 2 1 day in the solar calendar is May 27th of the lunar calendar, which is the summer solstice (mid-May); But July 23rd in the solar calendar is the first day of June in the lunar calendar, and this day is the summer heat (the qi of June). From June 24th to July 22nd of the Gregorian calendar (one month after the end of May of the lunar calendar), there is only one solar term, and this month is leap May. Therefore, leap month is determined by people according to certain laws, which is not mysterious.