So, what's the difference between the lunar calendar and the lunar calendar, and the solar calendar?
Let me talk about the solar calendar first. After the Revolution of 1911, China began to adopt the western Gregorian calendar, namely the solar calendar. The solar calendar is based on the law that the earth revolves around the sun. The earth revolves around the sun 1 circle every 365 days, 5 hours, 48 minutes and 46 seconds, which is called 1 solar year. The solar calendar year stipulates that the big month is 3 1 day, the small month is 30 days, and the month is 1,1February is ***365 days or 366 days.
The lunar calendar is based on the law that the moon revolves around the earth. The moon is also called "lunar calendar", so the lunar calendar is also called lunar calendar. The lunar calendar 1 month is called "Shuowangyue", and the first day of each month is Shuori, and the fifteenth day is Wangri. "Looking at the moon" is the average cycle of the moon's profit and loss. That's what the so-called "full moon, sunny and round" means. The lunar month is calculated according to the length of the first lunar month of 29.5306 days. In order to avoid decimals, it is stipulated that there are 30 days in the first lunar month and 29 days in the second lunar month. In order to ensure that the first day of each month must be a new moon, the arrangement of large and small months is not fixed and needs to be determined through strict observation and calculation. Therefore, it is common for the lunar calendar to be big and small for two consecutive months, and even there are rare exceptions such as March and April of 1990. September, 10,1month and1February are big for four consecutive months.
It is not difficult to see that 1 lunar year is about less than 1 sun is young 1 day, and it will be less than1month after three years. Over time, there will be disorder of time sequence and time. For example, the Spring Festival in one year of the lunar calendar is a cold winter, and the Spring Festival in the second year will be earlier than the season 1 1 day, and the Spring Festival in 16 will appear in the hot summer, which is very embarrassing.
However, this has never happened, because there is a great invention in China's calendar called "leap method". Every 19 year, there are 7 leap months, and the year with leap months is 1 year, 383 days or 384 days, which is called leap year. For example, 20 16 and 2020 are leap years. There is a poem in Lu You's My Dwelling House, which is "Wheat grains are damaged by rain, and silkworms are late for leap years". This calendar, which has the characteristics of China, has leap months and takes into account the lunar calendar, is called the "lunar calendar" and its scientific name is "lunar calendar". China began to use the lunar calendar in the Xia Dynasty, so the lunar calendar is also called the summer calendar.
So, how long does it take to add 1 leap month? After calculation, 1 leap month is added every 3 years, 2 leap months every 5 years, 3 leap months every 7 years and 7 leap months every 19 years. After adding seven leap months to 19, the error is only over 2 hours and 9 minutes, which is accurate enough. The solar calendar and the lunar calendar are basically synchronized. Therefore, the lunar calendar adopts the method of 19 plus 7 leap months, that is, "19 7 leap months", which well coordinates the solar year and the lunar year, so that the Spring Festival of the lunar calendar is always kept in the late winter and early spring, and the average length of the lunar year is close to that of the solar year. Moreover, the moon in the lunar calendar has distinct moon phase characteristics, so the lunar calendar has the characteristics of killing two birds with one stone.
The setting of lunar leap month is related to the 24 solar terms. Twenty-four solar terms are based on the solar calendar, and there are two fixed solar terms every month. The date of the 24 solar terms in the lunar calendar is not fixed, but postponed month by month, so in some lunar months, the gas falls at the end of the month and will be exhausted next month. Generally, there will be one month out of breath every two years, which coincides with the year when leap month is needed. Therefore, the lunar calendar stipulates that non-neutral months are leap months. For example, April 29th of 200 1 lunar calendar is full of qi, and the first day of 1 month is the next summer solstice in Qi. Where 1 month is defined as leap month, after April, so it is called leap April. It can be seen that which month of the lunar calendar leap depends entirely on the 24 solar terms in a year.
It should be pointed out that the insertion of the lunar leap month is completely artificial. The placement of leap months in different dynasties is also different. Before the Qin Dynasty, there was a time when the leap month was placed at the end of a year, which was called "March". The leap month in the early Han dynasty was placed after September, which was called "post-September". In the first year of Emperor Wu of the Han Dynasty, the month without neutral gas was defined as the leap month of the previous month, and the word "leap" was added to the name of last month, which has been in use ever since. The statistics of the astronomical department also found that the distribution of leap months is irregular.