How are the 24 solar terms divided?

Solar terms refer to the 24 solar terms and climate, which is a calendar invented by China in ancient times to guide farming. In ancient China, the sundial was measured by earth gauge, and the longest sun shadow was defined as the sun solstice (also called sun solstice, sun solstice and summer solstice), and the shortest sun shadow was defined as the sun solstice (also called short solstice and winter solstice). In the Spring and Autumn Period, there was a day with the same length of day and night, which was defined as vernal equinox and autumnal equinox. There were only four solar terms in the Shang Dynasty, and eight in the Zhou Dynasty until the Western Han Dynasty. The concepts of yin and yang, four seasons, eight places, twelve degrees and twenty-four solar terms are mentioned in the preface to Historical Records.

Each of the 24 solar terms corresponds to a certain position reached by the sun every time it moves 15 on the ecliptic. The twenty-four solar terms are divided into 12 neutral solar terms and 12 solar terms, which correspond to each other one by one. The twenty-four solar terms reflect the annual apparent motion of the sun, so their dates are basically fixed in the Gregorian calendar. The solar terms in the first half of the year are on the 6th, the solar terms in the second half of the year are on the 8th and the solar terms are on the 23rd, with a difference of less than 1 ~ 2 days.

Divide the length of a tropical year into 24 parts on average, and arrange all neutral gases and solar terms at equal intervals in turn from winter to Sunday. This method is called flat gas. Due to the uneven annual apparent motion of the sun, the solar terms of each shift of the ecliptic 15 degrees are not equidistant, which is called constant qi. Fixed air is used in calendar calculation. Because the time of two solar terms is longer than that of a new moon (see the moon), there may be only one solar term or a neutral atmosphere in a month. Since taichu calendar in the Western Han Dynasty, it has been stipulated that the month without neutral gas is the leap month of last month. This principle of setting leap is still in use today.

The naming of the twenty-four solar terms reflects three seasons, climate phenomena and climate change. The reaction seasons are beginning of spring, Spring Equinox, Long Summer, Summer Solstice, beginning of autumn, Autumn Equinox, beginning of winter and Winter Solstice, also known as Eight; Weather phenomena are amazing, clear, rich and complex. There are rain, Grain Rain, slight heat, great heat, Chu heat, white dew, cold dew, first frost, light snow, heavy snow, slight cold and severe cold.

Modern people accurately determine the specific time of the 24 solar terms according to the position of the sun on the ecliptic.

Simply put, solar terms are calculated according to the solar cycle, and the solar calendar is completely compiled according to the solar cycle. China people can work it out because the lunar calendar takes into account the periods of the sun and the moon. Anyone in China can make good use of it. We can also see the wisdom of the people of China.