Winter solstice is the key solar term of yin and yang.

The days and personnel change rapidly every day, and then the winter solstice, after the winter solstice, after the weather gets warmer, spring comes back. -Today is the winter solstice.

The ancients said this about the winter solstice: As soon as the cathode arrived, the yang began to grow, the sun went south, the day was short and the shadow was long, so it was called "the winter solstice". Since the winter of November, the days have been getting longer and longer, and the yang of heaven and earth has become stronger and stronger. Therefore, the solstice in winter represents the beginning of the next cycle, which is a good day. But at this time, the weather will not get warmer, because the cold air absorbed by the earth will not be released until the winter solstice. Although the sun is a spirit, the cold of the northern land has just begun!