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Solar terms, also called Jieqi in Chinese, are days marking one of the 24 time buckets of the solar year in traditional Chinese calendar, and were used to indicate the alternation of seasons and climate changes in ancient China. It is a unique component and creative invention of Chinese traditional calendar.

China’s 24 solar terms was added to the United Nations Educational, Scientific and Cultural Organization’s (UNESCO) world intangible cultural heritage list on November 30. The announcement was made during the 11th session of UNESCO’s Intergovernmental Committee for the Safeguarding of Intangible Cultural Heritages in Addis Ababa, Ethiopia's capital.
China currently has 39 different items on UNESCO's intangible cultural heritage lists. Since 2008, 31 items have been included on the Representative List of the Intangible Cultural Heritage of Humanity.

Origin of 24 Solar Terms

The Yellow River Basin, in northern China, is believed to be the cradle of the solar terms system. Ancient Chinese farmers used astronomical signs, changes in temperature and precipitation as the basis to create the calendar, which was later adopted by multiple ethnic groups in different regions across China.

As early as the Spring and Autumn Period (770–476 BC), Chinese ancestors had already established two major solar terms, ri nan zhi (日南至 'Sun South Most') and ri bei zhi (日北至 'Sun North Most').

As of the end of the Warring States Period (475–221 BC), eight key solar terms (Start of Spring, Vernal Equinox, Start of Summer, Summer Solstice, Start of Autumn, Autumnal Equinox, Start of Winter and Winter Solstice) marking the four seasons, were established according to the different positions of the sun and changes in natural phenomena.

The rest of the solar terms were initiated in the Western Han Dynasty (206 BC–24 AD). Hence most terms refer to the climate of Xi'an, capital of the Han Dynasty.

General Introduction

China’s 24 solar terms is a knowledge system and social practice formed through observations of the sun's annual motion, and cognition of the year's changes in season, climate and phenology.

Ancient Chinese divided the Sun’s movement through the sky into 24 segments, with each segment equaling one roughly two-week-long “solar term”.

The 24 solar terms each suggests the position of the sun every time it travels 15 degrees on the ecliptic longitude. The 24 solar terms include Start of Spring, Rain Water, Awakening of Insects, Spring Equinox, Clear and Bright, Grain Rain, Start of Summer, Grain Buds, Grain in Ear, Summer Solstice, Minor Heat, Major Heat, Start of Autumn, End of Heat, White Dew, Autumn Equinox, Cold Dew, Frost's Descent, Start of Winter, Minor Snow, Major Snow, Winter Solstice, Minor Cold and Major Cold.

Classification of 24 Solar Terms
The 24 solar terms known as Start of Spring, Start of Summer, Start of Autumn, and Start of Winter are used to reflect the change of seasons, dividing the year into four seasons of exactly three months.

The solar terms of Vernal Equinox, Autumnal Equinox, Summer Solstice and Winter Solstice are divided from an astronomical aspect, reflecting the turning point of the variation of the altitude of the sun.

Minor Heat, Major Heat, Limit of Heat, Minor Cold, and Major Cold reflect the changes of temperature in different periods.

Clear and Bright, Rain Water, Grain Rain, Minor Snow, and Major Snow, White Dew, Cold Dew, and Frost Descent reflect the phenomenon of precipitation, indicating the time and intensity of rainfall, snowfall, dew, and frost.
Small Full (Grain) and Grain in Ear reflect the maturity and harvest time of crops, while Awakening of Insects reflects observed insect activity.

Application of 24 Solar Terms

Based on the sun’s position in the zodiac, the 24 solar terms, were created by farmers in ancient China to guide the agricultural affairs and farming activities. The 24 solar terms reflect the changes in climate, natural phenomena, agricultural production, and other aspects of human life, including clothing, food, housing, and transportation.

They serve as an instruction manual of sorts for farmers, allowing them to know what conditions to expect or what agricultural activities to carry out during certain periods of the year. They are often called China's “fifth great invention” after papermaking, printing, gunpowder and the compass.

Besides its role as an almanac, many of these solar terms have become associated with Chinese customs over the centuries, such as honoring one's ancestors for Qingming (Bright and Clear) in April or eating dumplings for Lidong (The Start of Winter).

For example the solar term Qingming, or Bright and Clear, is deeply tied to China's tradition of paying respects to one's ancestors and visiting the family tomb. For this reason, in English the Qingming Festival is often known as the Tomb-Sweeping Festival.

Contemporary Significance 

In the current time of technology-based modern farming, traditional solar terms remain relevant. It is also an important cultural existence in modern Chinese social life, serving as a reference in daily life, ancestor worship and others around seasons. Although in modern times it is not regarded as the major guiding knowledge in agriculture production, it remains the symbol of the evolving farming civilization relationship between people and nature. It can recall our memories and remind us that the nature is changing at its own pace. 24 solar terms is the crystallization of Chinese people in the relationship between human and nature.

To sum up, it is an indispensable component of the traditional Chinese calendars and its living applications, serving as a time-frame for agricultural activities and daily life. In international circle of meteorology, this cognitive system has been honored as the Fifth Great Invention of China.

This legacy reflects the Chinese people's respect for nature and tradition, their unique understanding of the universe, their wisdom to live in harmony with nature, and the world’s cultural diversity, said Zhang Ling, an official with the Ministry of Culture, who attended the UNESCO meeting in Addis Ababa.

Editor Liu Shuqiao