Twenty-four solar terms, a supplementary calendar that was established in China in the pre-Qin period and completely established in the Han Dynasty, is a knowledge system formed by observing the annual movement of the sun and recognizing the changing laws of seasons, climate and phenology in a year.

It divides the annual movement track of the sun into 24 equal parts, and each equal part is a solar term, which starts from the beginning of spring and ends in severe cold, and goes on and on. It is not only the time criterion promulgated by the government in past dynasties, but also the compass to guide agricultural production. The compass for people to predict the cold and warm snow and rain in daily life is the crystallization of the long-term experience and wisdom of Han working people.

In ancient China, the sundial was measured by Tugui, and the longest day shadow was defined as "solar solstice" (also known as long day solstice, long day solstice and winter solstice), and the shortest day shadow was "short day solstice" (also known as short day solstice and summer solstice). In spring and autumn, there is a day with the same length of day and night, which is designated as "vernal equinox" and "autumn equinox". There were only four solar terms in Shang Dynasty, but it developed to eight in Zhou Dynasty, and the twenty-four solar terms were completely established in Qin and Han Dynasties. In BC 104, taichu calendar, written by Deng Ping, officially set the 24 solar terms in the calendar, and defined the astronomical position of the 24 solar terms.

The names of the twenty-four solar terms first appeared in Huai Nan Zi Tian Xun 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 of Historical Records Taishigong. During the reign of Emperor Wu of the Han Dynasty, Luo Xiahong compiled the solar terms into the taichu calendar, and stipulated that the month without neutral gas was the leap month of last month.

Twenty-four solar terms refer to 24 specific festivals in the China lunar calendar, which indicate seasonal changes. They are formulated according to the position changes of the earth on the ecliptic (that is, the earth's orbit around the sun), and each one corresponds to a certain position reached by the earth every movement15 on the ecliptic.

2. Significance

Twenty-four solar terms are not only the time criterion promulgated by the government in past dynasties, but also the compass to guide agricultural production, and the compass for people to predict cold, warm, snowy and rainy days in daily life. Twenty-four solar terms accurately reflect the seasonal changes and are used to guide agricultural activities, affecting the food, clothing, housing and transportation of thousands of households. The twenty-four solar terms scientifically reveal the laws of astronomical and meteorological changes.

Twenty-four solar terms skillfully combine astronomy, agriculture, phenology and folk customs, and derive a large number of related seasonal cultures, which have become an important part of Chinese traditional culture.

Twenty-four solar terms-China people's time knowledge system formed by observing the annual movement of the sun and its practice "was officially listed in the representative list of human intangible cultural heritage.

20 16 1 1 October 30th, the first regular session of UNESCO's Intergovernmental Committee for the Protection of Intangible Cultural Heritage1/approved the inclusion of "Twenty-four solar terms-China people's time knowledge system formed by observing the annual movement of the sun and its practice" declared by China.

There is a process to protect the 24 solar terms in China. In 2006, the twenty-four solar terms of the lunar calendar were listed in the first batch of national intangible cultural heritage representative projects, and in 201year and 201year, Jiuhua beginning of spring Festival, Ban Chun to persuade farmers, Shiqian to say spring, Sanmen to worship winter, Zhuang first frost Festival, Miao to catch autumn and Anren to catch branches were also listed in this heritage project.

Twenty-four solar terms are listed in the representative list of intangible cultural heritage of mankind, which reflects the importance that the international community attaches to the protection of intangible cultural heritage of traditional knowledge and practice, and also means the recognition of this excellent cultural heritage and the trust that China undertakes the responsibility of protection. This requires our country to mobilize various social forces, take more organized and planned protection measures, and actively promote the protection of the 24 solar terms.