When did the lunar calendar begin at the earliest?

Twenty-four solar terms originated in the Yellow River Basin. As early as the Spring and Autumn Period, the ancient sages of our country set four solar terms, such as midsummer, midsummer, midsummer and midsummer, and constantly improved and perfected them. By the Qin and Han Dynasties, the 24 solar terms had been completely established. In BC 104, the taichu calendar written by Deng Ping officially set 24 solar terms in the calendar, and defined the astronomical position of the 24 solar terms. Twenty-four solar terms are the original cultural heritage of working people in China, which can reflect the changes of seasons, guide agricultural activities and affect the food, clothing, housing and transportation of thousands of households.

As early as the Spring and Autumn Period and the Warring States Period, China was able to measure the length of the sun's shadow at noon with a soil gauge (a pole was erected on the plane), thus determining four solar terms: winter solstice, summer solstice, vernal equinox and autumn equinox. In a year, the shortest day of the noon soil return shadow is the summer solstice, the longest day is the winter solstice, and the shadow with moderate length is the vernal equinox or autumn equinox. The Book of History in the Spring and Autumn Period recorded the solar terms. The twenty-four solar terms are completely recorded in Huainanzi written by Liu An in the Western Han Dynasty. In ancient China, the lunar calendar was used to record time, and the solar calendar was used to divide the 24 solar terms of spring, summer, autumn and winter. Our ancestors called every five days and every three days as solar terms, and a year was divided into 72 days out of 24 solar terms.

With continuous observation, analysis and summary, the division of solar terms is gradually enriched and scientific. By the Qin and Han dynasties more than 2000 years ago, a complete concept of 24 solar terms had been formed.

24 solar terms is divided according to the position of the sun on the ecliptic (that is, the earth's orbit around the sun). Depending on the sun starting from the vernal equinox (longitude zero, at this moment the sun shines vertically on the equator), every advance of 15 degrees is a solar term; After a week's operation, I returned to the vernal equinox, which is a tropical year with 360 degrees, so it is divided into 24 solar terms. The time when the sun runs along the longitude of the Yellow River from zero 15 degrees is called "a solar term". It runs 360 degrees every year, and * * * experiences 24 solar terms, twice a month. It reflects the annual apparent movement of the sun, so the date of solar terms is basically fixed in the current Gregorian calendar. The first half of the year is on the 6th and 2nd1,and the second half is on the 8th and 23rd, with a difference of 1 ~ 2 days. Therefore, from this point, we can clearly analyze that although the 24 solar terms came from ancient China, their algorithms are basically consistent with the existing solar calendar. According to the position change of the sun on the ecliptic and the evolution order of the ground climate caused by it, the whole year is accurately divided into 24 equal parts, and each equal part is named.

Although the 24 solar terms are divided according to the Gregorian calendar, there will still be fluctuations for a day or two, but the changes are basically fixed. Take beginning of spring as an example: beginning of spring is always between February 3rd and 5th in the solar calendar every year. Similarly, for the first frost, the solar terms are also between 10 10 and 23/0, so the difference is still very small. However, in the lunar calendar, the date of solar terms is not easy to determine. Take beginning of spring as an example. It can be on the first day of February 15 of the 65438+ lunar calendar, or at the latest 15. As an important basis for guiding agriculture, the 24 solar terms must be relatively accurate. Therefore, if it is divided according to the lunar calendar, it will inevitably bring great errors, and of course it will not play a role in guiding information in time.

There are many kinds of calendars in the history of the world, but they can be roughly divided into the following three types: one is called the solar calendar, the average number of days in a year is about the tropic of Capricorn, and the number of days and months in a month is artificially specified, such as the Gregorian calendar and julian calendar; One is called lunar calendar, and the number of days in a month is about equal to the first month, while the number of months in a year is artificially specified, such as Islamic calendar and Greek calendar. The other is called the lunar calendar. The average number of days in a month is about equal to Wang Shuo, and the average number of days in a year is about equal to the Tropic of Capricorn, such as the lunar calendar and Tibetan calendar in China.

Lunar calendar is a traditional calendar adopted in China, with 24 solar terms guiding agricultural activities, which are mainly used in the vast rural areas, so it is called lunar calendar. Also known as the summer calendar, the old calendar and the lunar calendar, some people call it the lunar calendar. It uses the strict lunar period to determine the month, and sets the leap month to make the average length of a year close to the tropic year, which has the attributes of lunar month and solar year, so it is essentially a yin-yang calendar.