Legacy of ancient wisdom in 24 solar terms
Editor's note:
The United Nations has officially designated 44 Chinese traditions as world cultural heritage. This series examines how each of them defines what it means to be Chinese.
The 24 solar terms, originating in ancient China, integrate astronomy, farming, phenology and folklore. They greatly influenced Chinese life, promoted social progress, and are recognized globally as a valuable cultural heritage, earning the title of "China's fifth great ancient invention."
Few cultural traditions have endured as precisely as the 24 solar terms. Rooted in ancient Chinese astronomical observations, the system is a cornerstone of traditional Chinese agrarian society.
The 24 solar terms are not just a testament to ancient Chinese ingenuity but also a reflection of connection between humanity and the natural world.
In 2016, 24 Solar Terms was inscribed by UNESCO as an Intangible Cultural Heritage of Humanity, underscoring their enduring significance.
Their origins can be traced back to ancient texts, with the earliest references found in the "Shangshu Yaodian," or the Book of Documents narrating the history of the reign of legendary Emperor Yao.
In Dunhuang, Gansu, a dragon dance marks the arrival of spring at the Mingsha Mountain and Crescent Lake Scenic Area.
The first complete documentation is found in the ancient philosophical book "Huainanzi," a collection of essays based on scholarly debates during the Western Han Dynasty (206 BC-AD 25).
By the Qin (221 BC-207 BC) and Han (202 BC-220 BC) dynasties, the system of 24 solar terms was fully established.
Under Emperor Wu of Han (156 BC-87 BC), 24 solar terms were officially incorporated into the Taichu Calendar, providing essential guidance for agricultural activities in the Yellow River basin.
A farmer in Yichang, Hubei Province, tills the fields and plants seedlings on Lixia, or the Beginning of Summer.
Science behind solar terms
The 24 solar terms divide the Earth's 360-degree orbit around the Sun into 24 equal segments, each marking a pivotal moment in the agricultural calendar.
The fourth solar term Chunfen, or spring equinox, marks the 0-degree point, and each subsequent 15-degree interval corresponds to a new solar term.
The first solar term is Lichun, or Start of Spring, whilst the last is Dahan, or Major Cold.
The Taosi Site Museum in Xiangfen County in Shanxi Province.
Taosi Relics Site: earliest tangible evidence of the 24 solar terms
The earliest tangible evidence of the 24 solar terms lies in the Taosi Relics Site in Xiangfen County in north China's Shanxi Province.
The site was discovered in 1958 and officially excavated in 1978. Over 5,500 artifacts have been unearthed, revealing the early forms of Chinese civilization. It serves as a key point in the empirical history of Chinese civilization over 5,000 years.
It also offers a glimpse into the astronomical practices of ancient Chinese societies. Archeologists have uncovered a large rammed-earth observatory at the site, believed to be China's oldest astronomical observatory.
Archeologists uncover a large rammed-earth observatory at the Taosi Relics Site, believed to be China's oldest astronomical observatory.
The observatory, once reconstructed, consists of 13 towering rammed-earth pillars arranged in semicircle, creating 12 observation gaps. At its center lies a circular observation point.
On specific solar term days, sunlight passes through a designated gap. During the winter solstice, for example, sunlight beams through the second gap. At the spring and autumn equinoxes, it shines through the seventh gap. At the summer solstice, it illuminates the twelfth and final gap.
Interestingly, modern observations reveal slight deviations in the sun's alignment with these slits. For instance, during the summer solstice, part of the Sun is hidden by the twelfth gap's southern pillar.
Experts attribute the shift to changes in the Earth's axial tilt over millennia, a fact that underscores the accuracy of ancient Chinese astronomers.
People witness sunrise at the Taosi Relics Site during the summer solstice.
Festivals rooted in the 24 solar terms
The 24 solar terms are deeply intertwined with Chinese festivals and traditional customs.
Some of the most notable celebrations include Qingming Festival, or Tomb-Sweeping Day, the Frost's Descent Festival of the Zhuang ethnic group, and the Beginning of Spring in Jiuhua Village of Quzhou in Zhejiang Province. All of them are listed as national intangible cultural heritage.
Whipping an ox is one of the key rituals on Lichun.
Beginning of Spring in Jiuhua
Lichun, or Beginning of Spring, is the first of the 24 solar terms. Falling between February 3 and 5, it marks winter's end and the arrival of spring.
In Jiuhua Village, the Jiuhua Lichun Festival is a cherished tradition around the Wutong Temple. On this day, locals welcome the God of Spring, Gou Mang, and pray for a bountiful harvest.
Key rituals include whipping an ox, symbolizing the start of farming, and offering incense and performances to honor the gods.
Local people also "seek spring" by visiting the Wutong Temple and "gather spring" by collecting evergreen branches. They "taste spring" by eating fresh greens. Children would wear wreaths of willow and bamboo for health.
People mourn the departed during the Qingming Festival.
Qingming Festival
Qingming Festival, which falls any day between April 4 and April 6, is both a solar term and a cultural tradition. As one of China's four major traditional festivals, alongside Spring Festival, Dragon Boat Festival, and Mid-Autumn Festival, it embodies the balance between remembrance and renewal.
Originally, Qingming was merely a solar term indicating the crisp air and vibrant scenery in springtime and the time for plowing and sowing. Its transformation into a day of ancestor veneration is closely tied to the Hanshi Festival, literally cold food festival. By the Song (960-1279) and Yuan (1271-1368) dynasties, Qingming had fully taken over as the primary day for honoring the departed.
The festival is mostly recognized for the practice of tomb-sweeping, where families clean gravesites, offer food and incense, and burn joss paper as an expression of respect and remembrance.
Qingming Festival is also a time to embrace the vitality of spring. People take part in outdoor excursions, fly kites and plant trees.
Food customs vary across regions, but Qingtuan, a green glutinous rice dumpling, remains one of the festival's most iconic delicacies.
Qingming Festival is also a time to embrace the vitality of spring.
Frost's Descent Festival of the Zhuang ethnic group
Shuangjiang, or Frost's Descent, is the last solar term of autumn. Falling between October 23 and 24 each year, it marks a sharp temperature drop and the transition to winter.
For the Zhuang people in south China's Guangxi Zhuang Autonomous Region and eastern Yunnan Province, it is also the time for a grand celebration of the harvest.
People dance in Chongzuo, Guangxi Zhuang Autonomous Region, to celebrate the Frost's Descent Festival.
Originally a way to give thanks for a bountiful harvest, the festival evolved into a major cultural event with ancestor worship, folk performances and trade fairs.
During the Song Dynasty, it was a time for social gatherings, singing and commerce, while farmers honored their cattle by giving them three days of rest.
In the Ming Dynasty, the festival took on a heroic significance, commemorating Madam Wa, a Zhuang female warrior who defeated Japanese pirates on this day.
By the Qing Dynasty (1644-1911), it had become a bustling trade fair, drawing merchants from afar.
Today, the Frost's Descent Festival of the Zhuang ethnic group remains a vibrant expression of gratitude and cultural pride, blending ancient traditions with the rhythms of nature and community.
