It's from The Complete Collection of Ancient and Modern Medical Systems by Xu Chunfu, a Ming Dynasty physician.
To itself also has two meanings, one is arrival and arrival; The other layer is poles and maxima.
Extended data:
Winter solstice, also known as solstice, sub-year, etc. It has both natural and humanistic connotations. It is not only an important solar term among the 24 solar terms, but also a traditional folk ancestor worship festival in China.
The solstice in winter is one of the eight festivals in four seasons, and it is considered as a big holiday in winter. In ancient times, there was a saying that the winter solstice was as big as a year. The custom of winter solstice varies in content or details due to different regions. In southern China, there are customs of offering sacrifices to ancestors and enjoying the winter solstice. In northern China, it is a custom to eat jiaozi from winter to Sunday every year.
The winter solstice is the 22nd solar term among the 24 solar terms, with a solar calendar of 270 degrees. It is celebrated every year on the Gregorian calendar of 65438+February 2 1-23. The solstice in winter is the extreme point of direct sunlight spreading to the south. From winter to the sun, the sun shines directly on the tropic of Capricorn, and the sun is most inclined to the northern hemisphere, and the elevation angle of the sun is the smallest. In all parts of the northern hemisphere, the days are the shortest and the nights are the longest.
The solstice in winter is also the turning point when the direct point of the sun returns to the north. The direct point of the sun moves northward from the tropic of Capricorn, and the daytime in the northern hemisphere will increase day by day.
References:
Baidu encyclopedia-winter solstice