Three months of winter imply the season of storing. The water freezes and the earth splits. During this period, people should obey the following rules: do not disturb internal yang qi. Go to bed early and get up late—later than the sunrise. Hide the emotions like an army ambushing, the birds hiding in trees or fish in rivers, keeping privacy, and having obtained something in mind. People should keep away from cold while staying close to warmth. Sweat little to avoid losing the yang qi from the skin pores. These all serve as the principles that conform to the winter and help maintain the hiding and storing functions of the human body.

                     --The Yellow Emperor's Inner Classic (Huáng Dì Nèi Jīng)

In the folk tradition, people used to consider the “Beginning-of-Winter Day” as the beginning of winter. A bleak visage of winter is displayed with fallen leaves and hibernated animals. In fact, the vitality of all the creatures has merely been hidden. Although the overground part of the trees on the earth has withered, the roots under the ground are still full of energy. Animals’ hibernation is to reduce their consumption and preserve their life energy. At this time, the movement trend of yang qi in the natural world is descending and latent.

Therefore, “hiding” or “storage” is a characteristic of winter. Correspondingly, the yang qi of the human body in winter is also restrained, descended, and stored in the kidney. In line with the principle of hiding and storing in winter for yang qi, the core of the “health preservation” is not to disturb yang, that’s, not to interfere with the hiding and storing of yang qi.

The six solar terms in winter are: Beginning of Winter, Slight Snow, Great Snow, Winter Solstice, Slight Cold, and Great Cold.