Twenty-four solar terms of the lunar calendar

In essence, solar terms belong to the solar calendar. From the astronomical point of view, the 24 solar terms are divided into 24 equal parts according to the 360-degree revolution of the earth around the sun (ecliptic), and the spring is divided into zero points. The two bisectors are separated by 15 degrees, and each bisector has a proper name, which contains the significance of climate change, phenological characteristics and crop growth. The 24 solar terms are beginning of spring, Rain, Surprise, Equinox, Qingming, Grain Rain, Long Summer, Xiaoman, Busy, Summer Solstice, Slight Summer, Great Summer, beginning of autumn, Chushu, Millennium, Equinox, Cold Dew, Early Frost, beginning of winter, Light Snow, Heavy Snow, Winter Solstice, Slight Cold and Severe Cold. In this order, all the single rooms are "solar terms", usually called "solar terms", while the double rooms are "neutral gas", referred to as "qi", collectively referred to as "solar terms". Now it is generally called twenty-four solar terms.

Twenty-four solar terms have been gradually established and improved in China. During the Zhou Dynasty and the Spring and Autumn Period in China, the summer solstice, winter solstice, vernal equinox and autumn equinox were determined by measuring the sun's shadow with soil gauge. Soil regression measurement is to measure the length of the sun shadow at noon with a vertical pole. The twelve solar terms recorded in Lu Chunqiu in Qin Dynasty have increased to eight, namely, beginning of spring, Spring Equinox, Long Summer, Summer, beginning of autumn, Autumn Equinox, beginning of winter and Winter Solstice. There are also some records about the germination of solar terms, such as stinging, rain, slight heat, white dew and first frost: 1 month. The stinging insects began to vibrate, and it began to rain in February, and the slight heat came in May, and the white dew fell in July, and it began in first frost in September. By the Han Dynasty, Huainanzi Astronomical Training had a complete record of 24 solar terms, exactly the same as today. China has a song called "Twenty-four Solar Terms", which is widely circulated and widely known. The content is as follows:

Spring rains shake spring and clear valleys,

Summer is full, summer is summer, summer is summer.

Autumn dew and autumn frost,

It snows in winter, it snows in winter, and it's a little cold in winter.

In order to remember the order of the 24 solar terms, people each took a word and made it up.

It should be noted that the fourth word of each sentence in this song happens to be spring, summer, autumn and winter, which is the four seasons of the year. But what is even more surprising is that they represent the vernal equinox, summer solstice, autumn equinox and winter solstice respectively. The vernal equinox and autumnal equinox are as long as nights, while the summer solstice and winter solstice are the longest and shortest days. They just divide the four points in the solar year equally, that is, divide the four points of the earth's orbit around the sun equally. In other words, the 24 solar terms of the lunar calendar are closely coordinated with the solar calendar.