What do the 12 Chinese solar terms refer to?

There are 24 Chinese solar terms, not 12.

The 24 solar terms refer to the days of the year when the earth orbits the sun at 24 defined positions, and are a supplementary calendar established in ancient China for guiding agricultural activities. It is an important part of traditional Chinese culture and still plays an important role in the lives of Chinese people.

The twenty-four solar terms are, in order, spring, rain, hibernation, spring equinox, clearing, rain, summer, fullness, mango, summer solstice, summer heat, summer heat, autumn, summer solstice, white dew, autumn equinox, cold dew, frost, winter, snow, snow, winter solstice, small cold, big cold.

To make it easier to remember, people have compiled the "Twenty-four Solar Terms Song": spring rain startled spring and clear valley days, summer full of mango summer heat connected. Autumn dew fall frost fall, winter snow snow winter small big cold.

Expanded Information

The Chinese 24 Solar Terms are calculated according to the solar calendar, not the traditional Chinese lunar calendar:

The lunar calendar is defined according to the phases of the moon, i.e., the moon's orbit around the earth is one month, and 12 months (13 in leap years) are put together and called a year. The solar calendar is defined by the seasons, which means that the Earth orbits the Sun in one year, and the year is divided into 12 roughly equal chunks, each of which is called a month.

Both the lunar and the solar calendars have their flaws, and it is a flaw that cannot be perfected to this day. The old Chinese calendar was not entirely lunar, the technical term for this is "yin-yang calendar".

The purely lunar calendar was one year for every 12 months, so after a few years there would be a situation where January would fall on a summer day. In order to change this pattern, the use of intercalary months was adopted, so that once a lunar date fell outside of a certain range of the seasons, the intercalary month was used to drag it back so that it did not deviate too much.

So the festivals in the current calendar date is basically fixed, each year before and after the gas is not different from 1 to 2 days, rather than with with the lunar calendar date corresponds to. The twenty-four solar terms originated in the Yellow River basin. As far back as the Spring and Autumn Period, the four solar terms of mid-spring, mid-summer, mid-autumn and mid-winter were set.

Thereafter, it was continuously improved and perfected, and by the Qin and Han dynasties, the 24 solar terms had been fully established. In 104 B.C.E., the Tai Chu Calendar, which was drawn up by Deng Ping and others, formalized the 24 solar terms in the calendar and clarified the astronomical positions of the 24 solar terms.

The twenty-four solar terms reflect the annual visual movement of the sun, so the dates of the solar terms are basically fixed in the current calendar, with the first half of the year on the 6th and 21st, and the second half of the year on the 8th and 23rd, with no difference of 1~2 days between the previous and the next.?

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