Have you found out that most people's solar and lunar dates on their 19th birthday coincide with or differ by one day from those when you were born. Do you know what this is about? In fact, the Chinese ancients were very intelligent. Do you understand the nineteen year seven leap?

In fact, the Chinese lunar calendar is a very advanced Yin Yang calendar. The so-called Yin Yang calendar is an advanced calendar that can reconcile the return year and the new moon at the same time. Here, readers can simply understand the regression year as the earth's cycle around the sun. More precisely, it refers to the time interval between two successive equinox passes by the center of the sun in the ecliptic. Due to the existence of precession, the equinox itself has a slow retrogression relative to the background star. Therefore, the regression year is slightly shorter than the stellar year experienced by the earth when it really revolves around the sun (the difference is about 20 minutes and 24 seconds). As for the new moon, as the name suggests, it refers to the time interval between the phases of the moon from one new moon (or new moon) to the next. Modern astronomical observations show that the average length of a regression year is about 365.2422 days, and the length of a new moon is about 29.5306 days, both of which are very fragmentary decimals. The number of year, month and day can only be an integer. How to use the rational number composed of these three groups of integers to approximate the above two irrational numbers has become the primary problem faced by calendar makers. In fact, according to the research of the Japanese astronomer Xincheng Xinzang, at least in the late spring and Autumn period, China had already explored a set of mature and ingenious plan for the reconciliation of the lunar calendar and the lunar calendar, that is, to prevent the year-on-year drift of the year's beginning in the solar calendar by means of 'setting the leap moon'.

By dividing the number of days in the regression year by the number of days in the new moon, we can calculate the number of new moon months in a regression year, which is about 12.36826 months. In addition to the 12 months in the integral part, there is also a decimal part, which is the source of the shift of the Eid al Fitr. The Chinese found that this decimal can be approximated by 7 / 19, and its value is about 0.36842. The first three significant digits of the two are the same. This means that only seven leap months every 19 years (that is, seven of the 19 years contain 13 new moon months, and the other 12 years contain 12 new moon months) can make the regression year and the new moon exactly reconcile. In the west, this intercalation method was first discovered by the ancient Greek astronomer meton of Athens in 432 B.C. and made public at the Olympic Games of that year. Therefore, this method of intercalation is also known as "modongzhang".

So the next question is how to arrange these seven leap months in a 19-year cycle. The ancient civilizations of the East and the West split on this point. The earliest Mesopotamian civilization adopted the barbillonian calendar. The king would randomly announce the setting of leap month according to the situation, so the setting of leap month was chaotic. The Jewish calendar intercalation method used by Jews is relatively simple. They regard the equinox as the node of the solar year, and stipulate that the new moon where the equinox is located is the first month of each year. If the above situation is not met, a leap month will be inserted at the end of last year. China's intercalation method is a little more complicated, which is a mixture of China's unique 24 solar terms system (see Table 2), relatively speaking, it is a more scientific intercalation method.

In fact, the Chinese lunar calendar is a very advanced Yin Yang calendar. The so-called Yin Yang calendar is an advanced calendar that can reconcile the return year and the new moon at the same time. Here, readers can simply understand the regression year as the earth's cycle around the sun. More precisely, it refers to the time interval between two successive equinox passes by the center of the sun in the ecliptic. Due to the existence of precession, the equinox itself has a slow retrogression relative to the background star. Therefore, the regression year is slightly shorter than the stellar year experienced by the earth when it really revolves around the sun (the difference is about 20 minutes and 24 seconds). As for the new moon, as the name suggests, it refers to the time interval between the phases of the moon from one new moon (or new moon) to the next. Modern astronomical observations show that the average length of a regression year is about 365.2422 days, and the length of a new moon is about 29.5306 days, both of which are very fragmentary decimals. The number of year, month and day can only be an integer. How to use the rational number composed of these three groups of integers to approximate the above two irrational numbers has become the primary problem faced by calendar makers. In fact, according to the research of the Japanese astronomer Xincheng Xinzang, at least in the late spring and Autumn period, China had already explored a set of mature and ingenious plan for the reconciliation of the lunar calendar and the lunar calendar, that is, to prevent the year-on-year drift of the year's beginning in the solar calendar by means of 'setting the leap moon'.

By dividing the number of days in the regression year by the number of days in the new moon, we can calculate the number of new moon months in a regression year, which is about 12.36826 months. In addition to the 12 months in the integral part, there is also a decimal part, which is the source of the shift of the Eid al Fitr. The Chinese found that this decimal can be approximated by 7 / 19, and its value is about 0.36842. The first three significant digits of the two are the same. This means that only seven leap months every 19 years (that is, seven of the 19 years contain 13 new moon months, and the other 12 years contain 12 new moon months) can make the regression year and the new moon exactly reconcile. In the west, this intercalation method was first discovered by the ancient Greek astronomer meton of Athens in 432 B.C. and made public at the Olympic Games of that year. Therefore, this method of intercalation is also known as "modongzhang".

So the next question is how to arrange these seven leap months in a 19-year cycle. The ancient civilizations of the East and the West split on this point. The earliest Mesopotamian civilization adopted the barbillonian calendar. The king would randomly announce the setting of leap month according to the situation, so the setting of leap month was chaotic. The Jewish calendar intercalation method used by Jews is relatively simple. They regard the equinox as the node of the solar year, and stipulate that the new moon where the equinox is located is the first month of each year. If the above situation is not met, a leap month will be inserted at the end of last year. China's intercalation method is a little more complicated, which is a mixture of China's unique 24 solar terms system (see Table 2), relatively speaking, it is a more scientific intercalation method.