The winter solstice is the fourth solar term in winter, when the sun moves to 270 degrees of the yellow meridian. On this day, the sun shines almost directly on the tropic of Capricorn, which is the shortest day and the longest night in the northern hemisphere. The ancient book "Su Wen on subtle pulse" said: "On the 45th day of the winter solstice, the yang is slightly higher and the yin is slightly lower." It means that in the 45 days from this day to beginning of spring, the yang gradually rises, the yin gradually declines, the days gradually lengthen and the nights gradually shorten.
There are traditional winter solstice foods all over the country. Besides jiaozi glutinous rice balls, glutinous rice is also very common.