Why did the ancients think that "the winter solstice is as big as a year"?

First of all, let me talk about when the winter solstice is. The winter solstice (February 22nd or 23rd every year in the solar calendar) was a very important solar term in ancient China, and many places had the custom of the winter solstice. The winter solstice is the year with the shortest day and the longest night in the northern hemisphere. The ancients knew this phenomenon for a long time. Bai Juyi, a poet in the Tang Dynasty, famously said, "Why can't I sleep alone for the longest night?"

In ancient times, there was a saying that "the winter solstice is as big as a year", and its holiday customs have been passed down for nearly 3000 years, which is a valuable intangible cultural heritage. The ancients held a celebration ceremony on the solstice of winter. During the winter solstice of the Zhou Dynasty, there was a grand ceremony of "The Emperor ushered in the new year with three officials and nine ministers"; The winter solstice in the Han Dynasty was listed as the "Winter Festival", and the government wanted to have a holiday and held a congratulatory ceremony called "He Dong". It is recorded in the Book of Jin that in the Wei and Jin Dynasties, it was praised by countries and bureaucrats from winter to the sun, and "it was inferior to Zheng Dan"; The winter solstice in Tang and Song Dynasties was more lively. According to the "Old Stories of Wulin" carefully written by the Southern Song Dynasty, "Everyone takes celebrating the winter as the most important thing, and the horses and chariots are beautiful and fresh, and the five drums have filled the nine streets. Women's and children's costumes are dazzling, just like the New Year "; During the Ming and Qing Dynasties, the emperor would go to the "Ball Altar" in the Temple of Heaven on the solstice of winter to hold a grand ceremony to worship the heavens. With the development of the times, many winter solstice folk customs have disappeared today. Only the diet custom from winter solstice has not been forgotten by contemporary people: on this day from winter solstice, northerners are used to eating jiaozi and wonton, southerners drink red bean porridge and jiaozi, and some people like to eat hot pot on this day.

The solstice of winter is also very important to us now. Usually the old people at home will remind us what to eat. Then there is a feeling of Chinese New Year. What do you eat at home on the solstice of winter?