The 24 solar terms is a general name of the systemic set-up that includes 12 minor solar terms and 12 major solar terms. The ancient Chinese divided the circle of the yearly motion of the sun into twenty four equal segments. They then named each segment ‘a solar term’ or ‘jie qi’. These 24 solar terms were developed by ancient Chinese farmers by observing the sun’s annual motion and they used them to mark various natural variations, important seasons, and the weather. Read on to find out more about the 24 solar terms of the Chinese Lunar Calendar.

What are the 24 solar terms?

The Solar Terms is a calendar of 24 periods and climate changes that guide and control agricultural arrangements in ancient and modern China. Each solar term is determined by the position of the sun in the sky and each solar term lasts for approximately 15 days. All in all, the 24 solar terms reflect the climate in central China.

Generally, the division of the 24 solar terms fully considered the variation of natural phenomena including climate changes, seasons, and phenology. The main solar terms such as Start/Beginning of Winter, Start/Beginning of Autumn, Start/Beginning of Summer, and Start/Beginning of Spring are used to directly reflect the various changes of seasons. These 4 solar terms divide the year into 4 seasons that last for three months each.

Solar terms such as Winter Solstice, Summer Solstice, Vernal Equinox, and Autumnal Equinox, on the other hand, have been divided from an astronomical perspective. They simply reflect the exact turning point of the variation of the sun’s altitude. Along with that, solar terms such as Grain in Ear and Small Full (Grain) notify the Chinese on the maturity levels and harvest time of crops, while solar terms such as Awakening of Insects reflect observed insect activity in farms so that Chinese farmers can take action on their plants.

Other solar terms such as Major Cold, Minor Cold, Limit of Heat, and Major Heat have been divided based on the changes of temperature in different time periods, while solar terms such as Frost Descent, Minor Snow, Major Snow, Clear and Bright, Rain Water, Grain Water, White Dew, and Cold Dew reflect the concept of phenomenon of precipitation. These indicate important factors such as temperature changes, time and intensity of dew, frost, rainfall, and snowfall.

Solar Terms and their definitions

Starting from the ‘Vernal Equinox’, the 12 major solar terms are: Vernal Equinox, Corn Rain, Corn Forms, Summer Solstice, Great Heat, End of Heat, The Autumnal Equinox, Frost, Light Snow, Winter Solstice, Severe Cold, and Spring Showers. Each one of these twelve major solar terms falls on one of the twelve Luna months that are clearly designated by the 12 earthly branches in China.

When it comes to the minor solar terms after the Vernal Equinox, they are: Bright and Clear, followed by Summer Commences, then Corn on Ear, Moderate Hear, Autumn Begins, White Dew, Cold Dew, Winter Starts, Heavy Snow, Moderate Cold, Spring Starts, and Insects Awaken.

Based on the Earth’s structure and solar system analysis, the Sun moves throughout the year across the celestial sphere along a unique path known as the ecliptic. This path is measured in 360 degrees longitudes, and the twenty four solar terms divide this path into 24 equal segments with approximately 15 degrees of the sun’s longitude between each term.

At the Autumnal Equinox and the Vernal Equinox, the periods of day and night are always equal in length. During the Summer Solstice, the daylight period is much longer and during the Winter Solstice, the days are much shorter. These 4 were the first solar terms to be established and they helped people understand time and how it works. Thereafter, all the other solar terms were established according to the weather and agricultural activities that were carried out during a particular season.

To add to that, each major Lunar month found in the Chinese agricultural calendar contains a major solar term. Any lunar month that does not have a major solar term is automatically identified as the leap month of the previous month.

What was the 24 solar terms used to guide in the earliest days?

Considered the fifth greatest invention in China after paper-making, the compass, gun powder, and printing; the 24 solar terms were created by ancient Chinese farmers to guide specific farming activities and general agricultural activities in different parts of China. These terms significantly reflect changes in climate, agricultural climate, natural occurrences, and agricultural production. Along with that, the terms reflect important aspects of human life such as housing, clothing, food, and transportation- from their acquisition, to their preservation and improvement. Up to date, nearly all farmers in all parts of China rely on the 24 solar terms to decide what exactly they need to do in their fields.

In addition to that, the solar terms are associated with social and cultural aspects of China. For example, solar terms such as ‘Clear and Bright/Pure Brightness’ is marked as the ‘Tomb Sweeping Day’ when the Chinese honor the dead. Additionally, the ‘Start of Winter’ involves the eating of dumplings, the ‘Start of Autumn’ is welcomed by earing porridge, and the people in South China celebrate the ‘Frost Festival’ on the ‘Start of Spring’. All these festivals are greatly observed and the Chinese rely on the 24 solar terms to guide activities during festivals.

24 Solar Terms of the Lunar Calendar

The table below highlights the 24 Solar Terms of the Lunar Calendar China and outlines their meanings.