Every year from December 21st to 23rd in the Gregorian calendar. The winter solstice is the 22nd of the 24 solar terms in China. This day is the shortest day and the longest night in the northern hemisphere. The days get shorter as you go north, and the polar night phenomenon occurs in the Arctic. Elsewhere in the Northern Hemisphere, the winter solstice is also the day when the midday sun is at its lowest altitude all year.

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Historical origin: The names of the twenty-four solar terms first appeared in "Huainanzi Tianwen Xun" of the Western Han Dynasty. In the first year of Taichu (104 BC), Emperor Wu of the Han Dynasty formulated the " "Taichu Calendar" absorbed solar terms as a supplementary calendar to guide agricultural affairs, and stipulated that the month without Zhongqi should be the leap month of the previous month. During the inheritance and development, the twenty-four solar terms were included in the lunar calendar and became an important part of the lunar calendar to form the yin and yang calendar.

Astronomical phenomenon: Every year from December 21st to 23rd in the Gregorian calendar, the direct point of the sun travels to the extreme south. On this day, the sun’s rays directly hit the Tropic of Cancer (23°26′S), and the sun’s rays are most tilted towards the northern hemisphere. The solar angle is the smallest, making it the day with the shortest day and the longest night in the Northern Hemisphere. The winter solstice is also the turning point when the sun's direct point returns north. After this day, it will "turn back." The sun's direct point will begin to move north from the Tropic of Capricorn, and the daylight hours in the northern hemisphere will increase day by day.

Traditional customs: The Winter Solstice is also a traditional festival of the Chinese nation. It is said that "the Winter Solstice is as big as the New Year". Most parts of northern China eat dumplings on this day because dumplings have the effect of "removing the cold" This means that there is still a folk proverb that "if you don't serve dumpling bowls during the winter solstice, your ears will freeze off and no one will care". In the south, there is a custom of eating winter solstice rice dumplings and winter solstice noodles.