Continuous photos of the 24 solar terms.

Beginning of spring, Rain, Creeping, Vernal Equinox, Qingming, Grain Rain, Changxia, Xiaoman, Mangzhong, Summer Solstice, Xiaoshu, Dashu, beginning of autumn, Chushu, Bailu, Autumnal Equinox, Cold Dew, Chufrost, beginning of winter, Light Snow, Heavy Snow, Winter Solstice, Slight Cold and Severe Cold.

China's traditional summer calendar (lunar calendar) is a kind of "combined calendar of yin and yang", which is based on daily and monthly exercise. "Yin" is determined according to the first month of the lunar calendar, and "Yang" is determined according to the earth's revolution around the sun from the winter solstice. A tropical year is about 365.2422 days, and the 24 solar terms are divided accordingly.

Twenty-four solar terms are special festivals in the calendar to express natural rhythm changes and establish "December construction". Four years old, three months in spring, summer, autumn and winter, two solar terms each month, each solar term has its own unique meaning. Twenty-four solar terms accurately reflect the change of natural rhythm and play an extremely important role in people's daily life.

It is not only a seasonal system that guides agricultural production, but also a folk system that contains rich folk customs. The twenty-four solar terms contain a long cultural connotation and historical accumulation, and are an important part of the long history and culture of the Chinese nation.

"Twenty-four solar terms" is the product of ancient farming civilization. It is a knowledge system formed by ancient ancestors following the farming season and observing the movement of celestial bodies to understand the changing laws of seasons, climate and phenology in a year. The twenty-four solar terms were originally formulated according to the changes of stars. The Big Dipper rotates once and bucket handle rotates once clockwise, which is called one of the "years" (Figure).

The current "twenty-four solar terms" are formulated according to the position of the sun on the return to the ecliptic, that is, the annual movement track of the sun is divided into 24 equal parts, each 15 is 1 equal part, and each 1 equal part is a solar term, starting from beginning of spring and ending from the severe cold. ?

Through historical development, the lunar calendar absorbed the solar terms of the dry calendar as a supplement to the calendar, and adjusted it to conform to the tropic year through the leap method, forming a combined calendar of yin and yang, and the "twenty-four solar terms" became an important part of the lunar calendar. In the field of international meteorology, the 24 solar terms are known as "the fifth invention of China".

In 20 16, UNESCO listed "Twenty-four solar terms-China people's time knowledge system formed by observing the anniversary movement of the sun and its practice" in the representative list of human intangible cultural heritage. The expanded list of intangible cultural heritage projects includes: Jiuhua Beginning Spring, Banchun Encouraging Agriculture, Shiqian Shuochun, Sanmen Winter Festival, Zhuang First Frost Festival, Miao Autumn Festival and Anren Branch Festival.