Why does the winter solstice solar term come at 18: 44?

Astronomy can be accurate to microsecond level. The winter solstice is the perihelion, when the angular velocity and linear velocity of the earth are the largest. At that point, the angle of the sun reaches the tropic of Capricorn.

The winter solstice is commonly known as "Winter Festival", "Dragon Solstice Festival" and "Asian New Year Festival". As early as more than 2,500 years ago in the Spring and Autumn Period, China had observed the sun with the earth and determined the winter solstice, which was the earliest of the 24 solar terms. The time is between 0 and 23 in Gregorian calendar 65438+February 265438. This day is the shortest day and the longest night in the northern hemisphere all year round; In most parts of northern China, it is also the custom to eat jiaozi and jiaozi on this day. Proverb: When winter solstice comes, eat jiaozi.

In ancient China, solar terms of the winter solstice were attached great importance. There was a saying that the winter solstice was as big as a year, and there was a custom of celebrating the winter solstice. "Han Shu" said: "The sun shines on the winter solstice, and you are long, so congratulations." The Book of Jin records: "On the winter solstice of Wei and Jin Dynasties, people from all over the world celebrated ... its appearance was not as good as that of Zheng Dan."