In the lunar calendar, why does beginning of spring have a specific beginning of spring time every year? For example, this year is 6: 48. How is this determined? Is there any pattern?

From a beginning of spring (in fact, any solar term is the same) to the next beginning of spring, it happens that the earth revolves once, and every minute is not bad. The period of revolution of the earth is 365.336 days, not an integer. So the beginning time of spring is different every year. However, the exact time when spring begins corresponds to the exact point of the earth's orbit. Therefore, beginning of spring Point, Summer Solstice Point, Winter Solstice Point and Great Cold Point can be marked on the Earth's orbit, and all the 24 solar terms have corresponding orbital points.

The current "Yellow River Longitude" solar terms are also based on precise astronomical calculations. "Twenty-four solar terms" (used since 1645) is divided into degrees of the ecliptic, and each solar term corresponds to a certain position reached by the sun every time it runs 15 on the ecliptic, reflecting the influence of the sun on the earth.

The degree method of the ecliptic (also called "the method of fixing qi") is a method to determine solar terms according to the position of the sun on the regression ecliptic, that is, on a 360-degree circle "ecliptic" (the sun's apparent path on the celestial sphere for one year), it is divided into 24 equal parts, each 15 is 1 equal part, and every 65438+.

It starts with the vernal equinox at 0 degrees (ranking first in beginning of spring) and is arranged according to the longitude of the Yellow River, that is, the sun starts from the longitude of the Yellow River at 0 degrees (at this time, the sun shines vertically on the equator), every advance 15 degrees is a solar term, and it returns to the vernal equinox after running for one week, which is a tropic year.