No matter four seasons and 24 solar terms of a year, or 24 hours of a day, they all have their own rules in transition.

The cycles of time and space and their relationship to human life and human well-being are very important in Chinese philosophy and medicine. These cycles were recorded and described based on both empirical observations passed down through the generations and conceptual frameworks that were a part of the worldview of the political, literary and religious elites in early China. 

This book, written by the periodical office of TCM Healthy Life-Nurturing (https://www.zyjkyszz.cn/), mainly elucidated health preservation based on time, consisted of three parts, involving health preservation in four seasons and 24 hours, as well as other traditional Chinese health maintaining methods such as music therapy and Five-Animal Exercises.

The book further illustrated the importance of the rhythms of time for the regulation of the human body regulation. It elucidated the basic rules or patterns of how yang qi waxes and wanes in the human body. For instance, "Yang qi in the human body primarily comes to the surface and protects the external part of the body in the daytime. In the morning, it grows and gradually becomes active; at noon, it reaches its peak; in the afternoon, it begins to decline and the sweat pores (Qi Men or openings for fluids and defense Qi) close up accordingly." In Chinese medicine, adapting to these changing rules of yin and yang by altering our lifestyle and wellness practices, healthy qi will grow stronger and be more able to resist pathogens. This is why health preservation can prevent diseases and keep the body strong and healthy.

In The Yellow Emperor's Inner Classic (Huáng Dì Nèi Jīng), the classical Chinese medical work from the Han dynasty that records the foundational ideas of the medicine, we find detailed descriptions of the correlation between the human body and the changes of yin and yang in the natural environment and the cosmos. For instance, it states that "Changes of yin and yang and the four seasons are the root of all things in nature," and "The human body is closely related to the heaven and earth and corresponds to the movement of the sun and the moon." Therefore, in terms of health preservation, it asserts that people should follow the rules of nature such as the four seasons, diurnal changes, and movement of the moon.