What is the lunar calendar

1. The origin of the solar calendar:
The solar calendar is the solar calendar, also known as the Gregorian calendar, which is internationally used. China has adopted the solar calendar since the first year of the Republic of China. In order to be symmetrical with the old calendar, the solar calendar is also called the "new calendar". The solar calendar is defined as a year by the time when the earth goes around the sun once. A total of 365 days, 5 hours, 48 minutes and 46 minutes. In ordinary years, only 365 days are counted, excluding the mantissa. The Gregorian calendar is divided into 12 months every year, with 31 days in the big month, 30 days in the small month, and only 28 days in February. It also stipulates that before July, a single month is a big month and a bimonthly month is a small month; After August, bimonths are big months, while single months are small months. The remaining 5 hours, 48 minutes and 46 seconds of each year are only about one day in four years. This day is added to February of the fourth year. This year is called the leap year, so February of the leap year has 29 days.
2. Determination of leap year in the solar calendar:
Generally speaking, when the year of the Gregorian calendar is removed by 4, the leap year can be completely divided. For example, 1984 and 1988 are leap years. However, because the exact number of days in the Gregorian calendar year should be 365 days, 5 hours, 48 minutes and 46 seconds, which is 5 hours, 48 minutes and 46 seconds more than 365 days in a normal year. A total of 23 hours, 15 minutes and 4 seconds more than 365 days in a normal year. If one leap plus one day every four years, it will be 44 points more and 56 points less, and nearly three more days will be added in four hundred years. Therefore, three days will be deducted every four hundred years. Therefore, a supplementary provision was made: every solar calendar year is a hundred years, such as 1800, 1900, 2000, etc., which can be divided by 400, so it is not a leap year. But 2000 yuan is a leap year, because February has 29 days.
3. The origin of the lunar calendar:
The lunar calendar takes one full moon as a month, 29 and a half days in total. For the convenience of calculation, 30 days are custom-made for the big month, 29 days for the small month, and in the middle of December of the year, the big and small months generally alternate. The lunar calendar has about 365 days a year, and there is no difference between leap years.
The lunar calendar does not consider the movement of the earth around the sun, so there is no fixed time for the changes of the four seasons in the lunar calendar. It cannot reflect the seasons, which is a great disadvantage. In order to overcome this shortcoming, people later decided on a new calendar, the so-called Yin Yang Tai Calendar. The summer calendar (also called the lunar calendar or the lunar calendar) that is still used in China is the combination of yin and yang. Like the lunar calendar, it makes a month according to the time when the moon is round and missing once, that is, 30 days for the big month and 29 days for the small month. However, it uses the method of adding leap months to make the average number of days per year close to the number of days per year in the solar calendar to adjust the four seasons. The lunar calendar has a leap month every two or three years.
4. Determination of lunar leap month:
As for which month of the lunar calendar, it involves the solar term. It is just a traditional saying that there are 24 solar terms in a year. In detail, we should say that there are 12 solar terms and 12 medium qi in a year. It is stipulated which of the twelve meso qi belongs to which month: rain is the meso qi of the first month; The vernal equinox is the middle of February; Grain rain is the mid air of March; Xiaoman is the mid air of April; The summer solstice is the mid air of May; The heat is the heat of June; Heat treatment is the middle of July; The autumnal equinox is the middle of August; Frost is the mid air of September; Light snow is the mid air of October; The winter solstice is the mid air of November; The severe cold is the middle of December.
As for the months of each solar term, it is not certain. The average lunar month is a little more than 29 and a half days, but the interval from one moderate to the next is a little less than 30 and a half days. In this way, the mid qi will be delayed for one day month by month in the lunar month. At a certain time, the mid qi will not be in the middle of the month but move to the end of the month. If the next month is a small month, it is likely that there will be no mid qi this month, because the next mid qi will move to the beginning of the third month. The middle month is not neutral, even if it is the leap month of last month. Take the example of 1998: June 21 of the Gregorian calendar is the 27th day of May of the lunar calendar, which is the summer solstice (mid May); On the other hand, July 23 is the first day of the sixth month of the lunar calendar, which is the day of great heat (moderate heat in June). From June 24 to July 22 of the lunar calendar (the month after the end of May), there is only one solar term of light heat, and without moderate heat, this month is considered as leap month. So the leap month of the lunar calendar is determined by people according to certain rules, which is not mysterious.