Why should the solar calendar be used in the twenty-four solar terms?

Because the earth rotates once a day and revolves around the sun once a year. Solar terms are divided according to the orbit position of the earth around the sun and the angle formed by the oblique intersection of the earth's rotation axis (the connecting line between the north and south poles of the earth) and the orbit (the ecliptic plane).

The twenty-four solar terms are divided according to the position of the sun on the ecliptic (that is, the orbit of the earth around the sun). Depending on the sun 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. The dates of solar terms are relatively fixed in the solar calendar. For example, beginning of spring in the solar calendar always falls between February 3rd and 5th. However, in the lunar calendar, the date of solar terms is not easy to determine. Take beginning of spring as an example. It can be the first day of the lunar calendar in the previous year, 65438+February 15, and the latest is the first month, 15.

Extended data:

Twenty-four solar terms refer to the special festivals in the dry calendar that indicate the season, phenology, climate change and the establishment of "December construction". It was originally determined by the bucket handle direction of the Big Dipper, and bucket handle revolved around the east, south, west and north for a period of time, which was called one of the "years old", starting from the beginning of spring and ending in the great cold.

24 solar terms? They all include: beginning of spring, Rain, Creeping, Spring Equinox, Qingming, Grain Rain, Long Summer, Xiaoman, Mangzhong, Summer Solstice, Slight Summer, beginning of autumn, Early Summer, Millennium, Autumn Equinox, Cold Dew, Early Frost, beginning of winter, Light Snow, Heavy Snow, Winter Solstice, Slight Cold and Severe Cold.

Baidu encyclopedia-24 solar terms