The origin of solar terms

Twenty-four solar terms originated in the Yellow River Basin. As early as the Spring and Autumn Period, four solar terms were set, namely, mid-spring, mid-summer, mid-autumn and mid-winter. After continuous improvement and perfection, 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.

There were four solar terms in Shang Dynasty, namely midsummer, midsummer, midsummer and winter solstice. During the Zhou Dynasty, eight names of solar terms appeared. Han Dynasty is the first great development period after the reunification of China, and it is also an important period of economic and cultural exchanges between the North and the South.

The names of the twenty-four solar terms were first seen in Tian Zi Xun of Huainan in the Western Han Dynasty, and the concepts of yin and yang, four seasons, eight places, twelve degrees and twenty-four solar terms were also mentioned in the preface to Historical Records Taishi Gong.

In the first year of Emperor Wu of the Han Dynasty, namely 104 BC, astronomers such as Luo and others formulated a calendar, absorbing solar terms as a supplementary calendar to guide farming, and designated the neutral month as the leap month of last month.

All the year round begins with "four stands", and the so-called "stand" is the beginning. Beginning of spring, Changxia, beginning of autumn and beginning of winter represent the beginning and arrival of spring, summer, autumn and winter respectively. In order to express the characteristics of time series more accurately, the ancients divided the solar terms into four groups according to the weather and phenology: divided, arrived, opened and closed.

"Fen" means vernal equinox and autumnal equinox, which was called "dichotomy" in ancient times; "Solstice" is the summer solstice and the winter solstice, which was called "the second solstice" in ancient times. "Qi" refers to beginning of spring and Changxia, "Closed" refers to beginning of autumn and beginning of winter, and beginning of spring, Changxia, beginning of autumn and beginning of winter are collectively called "Sili", which add up to * * * to "eight sections". Corresponding to the most important "eight festivals" in the solar terms. If you choose the key points in the eight sections, it is the "second solstice" of the summer solstice and the winter solstice.

In winter solstice, the sun reaches the southernmost point, while in summer solstice, the sun reaches the northernmost point, which is what the ancients said: "The sun reaches the north, with long days and short shadows, so it is called summer solstice." Do your best.