How are the 24 solar terms calculated?

The twenty-four solar terms are divided according to the position of the earth on the ecliptic (that is, the earth's orbit around the sun). Depending on the sun starting from the vernal equinox (longitude zero, at this moment the sun shines vertically on the equator), every advance of 15 degrees is a solar term; After a week's operation, I returned to the vernal equinox, which is a tropical year with 360 degrees, so it is divided into 24 solar terms.

Second, the date calculation:

General formula of longevity -[y× d+c]-l

Y= the last two digits of the year, D=0.2422, L= the number of leap years, and C depends on the solar terms and year.

265438+20th century beginning of spring c value =3.87.

For example: beginning of spring date 20 17.

[ 17×0.2422+3.87]-[( 17- 1)/4]=7.9874-4=3

So the beginning of spring date of 20 17 is February 3rd.

(Note: Only integers are reserved for the calculation results)

Third, the solar terms:

There are twenty-four solar terms in a year, including twelve solar terms and twelve qi. In other words, there is a festival in a month, and the average interval between every two solar terms is about 30 days and 40 minutes, while the number of days in the lunar calendar is 29 and a half days. Therefore, every 34 months, there must be two months when there is no gas and no gas.

A month without knots is a leap month in the lunar calendar, and a month without knots is not a leap month.

Extended data:

I. Twenty-four solar term song

The plum blossoms in the early spring are particularly bright, and the apricot blossoms after the rain are particularly fresh;

Lulin thunder, butterfly dance between flowers at the vernal equinox.

Qingming kite broken, Grain Rain tender tea jade companion,

Mulberry fruits are like cherries in the long summer, and silkworms are cultivated in the small man.

Before mango seedlings enter the palace, the summer solstice rice and flowers are like white practice;

Summer breeze urges early-maturing beans, and Chi Pan enjoys red lotus in hot summer.

Beginning of autumn knows how to make people fall asleep, and sunflowers smile in summer.

The white dew returns to the geese, and the autumn equinox smells like osmanthus.

Cold dew vegetable seedlings are green, and the first frost reed flowers are floating all over the sky;

Beginning of winter reported good news, reported three rewards, and light snow and goose feathers flew in pieces.

The snow is very cold, the plum blossoms are crazy in the wind, and the winter solstice is full of snow.

Little cold wanderers are homesick, and they celebrate reunion at the end of the cold year.

Second, the influence of the twenty-four solar terms:

Twenty-four solar terms are not only the time criterion promulgated by successive governments, but also the compass to guide agricultural production and to predict cold, warm, snow and rainy days in people's daily life. Twenty-four solar terms accurately reflect seasonal changes, which are used to guide agricultural activities and affect the food, clothing, housing and transportation of thousands of households. The twenty-four solar terms scientifically reveal the laws of astronomical and meteorological changes.

Twenty-four solar terms skillfully combine astronomy, agriculture, phenology and folk customs, resulting in a large number of related seasonal cultures, which have become an important part of China traditional culture.

In the long farming society, the 24 solar terms have played an important guiding role in agricultural activities and have rich cultural connotations. Some important solar terms such as beginning of spring, Winter Solstice and Qingming also have interesting folk customs, such as "biting spring" and "hiking".

The 24 solar terms are still of practical value to our life and culture. For example, from the very popular Chinese medicine health care, autumn begins with the beginning of the autumn solar term, close to the great summer heat, hot and humid; Autumn ends in the first frost, close to the early winter, and the climate is dry and cold.

Although early autumn and late autumn are in the same season, the climate is completely opposite, and the seasonal diseases encountered by doctors are completely different from those that Chinese medicine needs to prevent. Therefore, it is not enough to simply follow the four seasons, but also follow the solar terms.

References:

Baidu encyclopedia-24 solar terms