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The 24 Solar Terms

Last updated by fabiowzgogo at 2015/5/19

The 24 solar terms, as a complementary calendar system invented and enacted in ancient China, refer to the twenty four periods which are used to guide agricultural affairs and farming activities in a year. The 24 solar terms are divided according to the sun’s position in the ecliptic plane (the orbit of the earth traveling round the sun). They came into being in Spring and Autumn Period and Warring States, reflecting the seasonal characteristics of annual natural phenomena and farming activities. The system plays an important part and has influenced greatly on people’s basic necessities of life.

The 24 Solar Terms

The 24 solar terms include the Beginning of Spring, Rain Water, the Waking of Insects, the Spring Equinox, Pure Brightness, Grain Rain, the Beginning of Summer, Grain Full, Grain in Ear, the Summer Solstice, Slight Heat, Great Heat, the Beginning of Autumn, the Limit of Heat, White Dew, the Autumnal Equinox, Cold Dew, Frost's Descent, the Beginning of Winter, Slight Snow, Great Snow, the Winter Solstice, Slight Cold and Great Cold.

The Origin

As far back as Spring and Autumn Period and Warring States, according to the moving position of the sun and the moon in the beginning and middle of a month, the climate and natural phenomena such as the growth of flora and fauna, people divided a year into 24 equal parts based on solar calendar and named them respectively, which is the origin of the 24 solar terms.

Meaning of 24 solar terms’ names

The 24 solar terms are divided according to the sun’s position in the ecliptic plane (the orbit of the earth traveling round the sun). The dates of the 24 solar terms are relatively fixed based on the solar calendar. However, the dates of solar terms according to the lunar calendar are not fixed. It can be perceived from the solar terms’ names that the division of the solar terms is made in full consideration of the variation of natural phenomenon such as seasons, climate and phenology.

The solar terms of the Beginning of Spring, the Beginning of Summer, the Beginning of Autumn and the Beginning of Winter are used to reflect seasons, which divides a year into four seasons including spring, summer, autumn and winter, marking the beginning of the four seasons in a year. The solar terms of the Spring Equinox, the Autumnal Equinox, the Summer Solstice and the Winter Solstice reflect the turning point of the variation of altitude of the sun based on astronomical aspect. As China is vast in territory, enjoying obvious monsoon and continental climate, the climate in different areas vary greatly and the variation of four seasons in different areas varies a lot. The solar terms of Slight Heat, Great Heat, the Limit of Heat, Slight Cold and Great Cold reflect temperature variations, indicating the temperature difference in different periods of a year. The solar terms of Rain Water, Grain Rain, Slight Snow and Great Snow reflect precipitation phenomenon, indicating the time and intensity of rainfall and snowfall. The solar terms of White Dew, Cold Dew and Frost's Descent reflect the course and degree of the gradual decrease of temperature.  The solar terms of Grain Full and Grain in Ear reflect the mature and harvest of crops. The solar terms of the Waking of Insects and Pure Brightness reflect the natural phenology phenomenon.

The Beginning of Spring, the Beginning of Summer, the Beginning of Autumn and the Beginning of Winter: mark the beginning of four seasons respectively. According to the Gregorian calendar, they are near Feb. 4th, May 5th, Aug. 7th and Nov. 7 respectively.

The Summer Solstice and the Winter Solstice: fall near Jun. 21 and Dec. 22 respectively according to the Gregorian calendar. It usually rains constantly in Summer Solstice and snows heavily in Winter Solstice. In Summer Solstice, the Northern Hemisphere has the longest daytime of the year and the Northern Hemisphere has the shortest daytime of the year in Winter Solstice.

The Spring Equinox and the Autumnal Equinox: fall near Mar. 20 and Sep. 23 respectively, with equal length in day and night according to the Gregorian calendar.

Rain Water: mark the beginning of precipitation and there is an increasing number of rainfall from then on, falling on about Feb. 18th the Gregorian calendar annually.

The Waking of Insects: the temperature picks up speed during this period and spring thunder appears. It is on March.5th based on the Gregorian calendar.

Pure Brightness: marks a change of weather, including the rising of temperature and the increasing of rainfall, indicating that spring ploughing should begin. As the temperature rebounds and it becomes warmer and comfortable day by day, people like to go for a spring outing during this period. It usually falls on Apr. 5th based on the Gregorian calendar annually.

Grain Rain: The rainfall increases greatly, which contributes to the growing of grain crops. It usually falls on April 20th based on the Gregorian calendar annually.

Grain Full: grain crops grow well, but not mature. It usually falls on May 21st based on the Gregorian calendar annually.

Grain in Ear: grain crops become mature and summer planting begins. It falls on Jun.5th based on the Gregorian calendar annually.

Slight Heat, Great Heat and the Limit of Heat: It is hot in Slight Heat and Great Heat is the hottest time of the year. Limit of Heat marks the end of hot summer days. They fall on Jul. 7th, Jul. 23rd and Aug. 23rd respectively every year.

White Dew: The temperature begins to drop and it turns quite cool. It falls on Sep. 7th based on the Gregorian calendar.

Cold Dew: The temperature becomes even lower and it becomes a little bit cold. It usually falls on Oct.8th according to the Gregorian calendar annually.

Frost's Descent: It gradually becomes cold and there is some frost, falling on Oct. 23rd according to the Gregorian calendar annually.

Slight Snow and Great Snow: It marks the beginning of snowfall. Slight Snow falls on Nov. 22nd and Great Snow falls on Dec. 7th according to the Gregorian calendar annually.

Slight Cold and Great Cold: It becomes even cold in Slight Cold and Great Cold is the coldest period of a year. Slight Cold falls on Jan. 5th and Great Cold falls on Feb. 20th according to the Gregorian calendar annually.