Introduction of Four Seasons and Twenty Four Solar Terms: Four Seasons Eight Solar Terms
✵Four Seasons, Eight Solar Terms, Twenty-Four Solar Terms, and the Seventy-Two Pentads in Spring, Summer, Autumn, and Winter are introduced. The Four Seasons, Eight Solar Terms, Twenty-Four Solar Terms, and Seventy-Two Pentads system is a traditional Chinese calendar system established in ancient China.
Four Seasons and Solar Terms
The Four Seasons, Eight Solar Terms, Twenty-Four Solar Terms, and Seventy-Two Pentads system is a traditional Chinese calendar system established in ancient China. The Four Seasons are known as: Spring, Summer, Autumn, and Winter.
The Eight Solar Terms are: (1) the Beginning of Spring, (2) the Spring Equinox, (3) the Beginning of Summer, (4) the Summer Solstice, (5) the Beginning of Autumn, (6) the Autumnal Equinox, (7) the Beginning of Winter, and (8) the Winter Solstice.
The Twelve Jieqi (the Twelve Node Solar Terms) are: the Beginning of Spring, Awakening from Hibernation, Pure Brightness, the Beginning of Summer, Grain in Ear, Lesser Heat, the Beginning of Autumn, White Dew, Cold Dew, the Beginning of Winter, Great Snow, and Lesser Cold.
The Twelve Zhongqi (the Twelve Central Solar Terms) are: Rain Water, the Spring Equinox, Grain Rain, Grain Buds, the Summer Solstice, Greater Heat, End of Heat, the Autumnal Equinox, First Frost, Light Snow, the Winter Solstice, and Greater Cold.
In ancient times, native Chinese people distinguished between the twelve Jieqi (the twelve node solar terms) and the twelve Zhongqi (the twelve central solar terms): the Jieqi were defined as the first solar term of each lunar month, while the Zhongqi were defined as the second solar term of the same lunar month. In modern times, they are collectively understood as the Twenty-Four Solar Terms. Five days constitute one pentad; each solar term comprises three pentads, resulting in a total of seventy-two pentads across the twenty-four solar terms—or equivalently, within one year.
The Twenty-Four Solar Terms are based on the Sun’s position along the ecliptic—the apparent path of the Sun across the celestial sphere, which corresponds to Earth’s orbital plane—and reflect seasonal changes. They guide agricultural activities and constitute an essential component of the traditional Chinese lunisolar calendar system.
Ever since the Eastern Zhou Dynasty (770–256 BCE.), including the Spring and Autumn Period (770–476 BCE) and the Warring States Period (475–221 BCE), the ancient Chinese people already had notions of Ri Nan Zhi (“the sun moves southward”) and Ri Bei Zhi (“the sun moves northward”). Later, observing phenomena and principles—such as the positions of the sun and moon at the beginning and middle of each lunar month, weather changes, and the growth cycles of animals and plants—ancient people gradually developed a system of solar terms. By the late Warring States Period, the book Lüshi Chunqiu already recorded the names of eight solar terms: Lichun (the Beginning of Spring), Chunfen (the Spring Equinox), Lixia (the Beginning of Summer), Xiazhi (the Summer Solstice), Liqiu (the Beginning of Autumn), Qiufen (the Autumnal Equinox), Lidong (the Beginning of Winter), and Dongzhi (the Winter Solstice). These eight solar terms are the foundational ones among the twenty-four solar terms and mark seasonal transitions, clearly dividing the year into four seasons. By the Qin Dynasty (221–206 BCE) and the Western Han Dynasty (206 BCE – 24 CE), the twenty-four solar terms system had been fully established. The ancient text Huainanzi already recorded the same twenty-four solar term names as those used in the modern system.
At the beginning of the Han Dynasty, the government still used the Zhuanxu Calendar, which had been established during the Qin Dynasty (221–206 BCE). However, this calendar contained certain inaccuracies. In 104 BCE, following advice from court astronomers—including Sima Qian—and others, Emperor Wu of Han ordered officials Deng Ping, Tang Du, and Luo Xiahong to develop a new calendar system, known as the Han Calendar. By 103 BCE, the new system was completed. In May of that year, Emperor Wu changed his reign title from Yuanfeng to Taichu; hence, the calendar became known as the Taichu Calendar. This new calendar explicitly incorporated the twenty-four solar terms and precisely recorded their astronomical positions.
The Taichu Calendar defined one year as 365.2502 days and one lunar month as 29.53086 days. It replaced the earlier "subtraction difference method" with the "additive difference method" to adjust time discrepancies. It shifted the first month of the year from the tenth lunar month (under the old Zhuanxu system) to the first lunar month (lunar January), thereby aligning the calendar more closely with agricultural needs. It also designated any lunar month lacking a "zhongqi" (mid-term solar term) as a leap month (intercalary month), thus resolving inconsistencies between the solar year and the lunar month count. This represented an epoch-making advancement in ancient Chinese calendrical science. Based on decades of astronomical observation and historical records, the Taichu Calendar also identified a 135-month solar eclipse cycle. Not only was the Taichu Calendar China’s first relatively complete calendar system, but it was also among the most advanced in the ancient world—officially adopted by the imperial government for nearly 189 years.
In ancient China, solar terms were called "qi." Each lunar month contains two qi: the first is called "jieqi" (sectional qi, or "solar term"), and the second is called "zhongqi" (central qi, or "mid-term solar term"). A brief introduction to the twenty-four solar terms follows. These terms are closely linked to the intercalation rules of the lunar calendar, and Lichun (the Beginning of Spring) serves as the first solar term in the sequence.
The names of the twenty-four solar terms originated from and were defined according to (1) the direction pointed to by the handle of the Big Dipper and (2) the natural climate and landscape characteristic of each period. The handle of the Big Dipper consists of three stars: Alioth (ε Ursae Majoris), Mizar (ζ Ursae Majoris), and Alkaid (η Ursae Majoris, also known as Benetnasch). As the Big Dipper rotates, its handle points toward different directions corresponding to the twelve earthly branches. For example: In lunar January—the first month of the lunar year, associated with the earthly branch yín ("寅")—at dusk, Alkaid points toward yín (i.e., the direction corresponding to 3–5 a.m.); at midnight, Mizar points toward yín; and during daytime, Alioth points toward yín. In lunar February—the second lunar month, associated with the earthly branch mǎo ("卯")—at dusk, Alkaid points toward mǎo (i.e., the direction corresponding to 5–7 a.m.); at midnight, Mizar points toward mǎo; and during daytime, Alioth points toward mǎo. Similar patterns apply to the remaining lunar months.
References:
1. Introduction of Four Seasons and Twenty Four Solar Terms: Four Seasons Eight Solar Terms
✵Four Seasons, Eight Solar Terms, Twenty-Four Solar Terms, and the Seventy-Two Pentads in Spring, Summer, Autumn, and Winter are introduced. The Four Seasons, Eight Solar Terms, Twenty-Four Solar Terms, and Seventy-Two Pentads system is a traditional Chinese calendar system established in ancient China.
Ever since the Eastern Zhou Dynasty (770–256 BCE.), including the Spring and Autumn Period (770–476 BCE) and the Warring States Period (475–221 BCE), the ancient Chinese people already had notions of Ri Nan Zhi (“the sun moves southward”) and Ri Bei Zhi (“the sun moves northward”). Later, observing phenomena and principles—such as the positions of the sun and moon at the beginning and middle of each lunar month, weather changes, and the growth cycles of animals and plants—ancient people gradually developed a system of solar terms. By the late Warring States Period, the book Lüshi Chunqiu already recorded the names of eight solar terms: Lichun (the Beginning of Spring), Chunfen (the Spring Equinox), Lixia (the Beginning of Summer), Xiazhi (the Summer Solstice), Liqiu (the Beginning of Autumn), Qiufen (the Autumnal Equinox), Lidong (the Beginning of Winter), and Dongzhi (the Winter Solstice). These eight solar terms are the foundational ones among the twenty-four solar terms and mark seasonal transitions, clearly dividing the year into four seasons. By the Qin Dynasty (221–206 BCE) and the Western Han Dynasty (206 BCE – 24 CE), the twenty-four solar terms system had been fully established. The ancient text Huainanzi already recorded the same twenty-four solar term names as those used in the modern system.
In ancient China, solar terms were called "qi." Each lunar month contains two qi: the first is called "jieqi" (sectional qi, or "solar term"), and the second is called "zhongqi" (central qi, or "mid-term solar term"). A brief introduction to the twenty-four solar terms follows. These terms are closely linked to the intercalation rules of the lunar calendar, and Lichun (the Beginning of Spring) serves as the first solar term in the sequence.
