Winter solstice is the most important solar term in health preservation, mainly because "winter solstice is born by the sun". According to the gossip theory, this time it is a complicated divination of mines. In the hexagrams, the top five are Yin and the bottom one is Yang, which symbolizes the birth of Yang. In ancient China, the winter solstice was designated as the second month, that is, the beginning of a year. Twelve o'clock a day, the child is also the time when the human body is born.

Ancient health care attached great importance to the birth of Yang. People think that when Yang is born, it should be carefully protected and nursed back to health, just like farmers' seedling raising and women's pregnancy, so as to make it grow sturdily. Because only when the yang in the human body is sufficient will the purpose of getting rid of diseases and prolonging life be achieved. Therefore, Zi Shi and Zi Yue play an important role in health preservation.

There are three versions of winter tonic: one is after beginning of winter and before beginning of spring; The second time is around the winter solstice; Three is three or nine days. Experts believe that the choice of winter tonic time varies from person to person. People with chronic diseases and yang deficiency need long-term tonic, starting from beginning of winter to beginning of spring; People who generally don't need a big tonic can concentrate on tonic in three to five days. Just as the folks have long said that "summer makes up for three volts, and winter makes up for three or nine". The solstice in winter is the beginning of counting nine, so people think it is best to put on makeup around the solstice in winter.