Library

The beginning and ending of the Six Qi (the six climatic factors: wind, cold, summer heat, dampness, dryness, and fire) may be early or late; the deficiency and excess of the Five Yuns (the five phases of movement: wood, fire, earth, metal, and water) are traced to ultimate principles and examined by precise numbers, thereby remaining unchanged for ten thousand generations. The Classics state: "Five days constitute one Hou (a period of time), corresponding to the Five Elements." Therefore, three Hou constitute one Qi (climatic phase), which is fifteen days. Three Qis constitute one Jie (solar term). The term "Jie" refers to the eight solar terms: Lichun (Start of Spring), Chunfen (Spring Equinox), Lixia (Start of Summer), Xiazhi (Summer Solstice), Liqiu (Start of Autumn), Qiufen (Autumn Equinox), Lidong (Start of Winter), and Dongzhi (Winter Solstice). The twenty-four solar terms distributed in the four directions govern the four seasons, completing one year. When the *Spring and Autumn Annals* mentions "Fen" (Equinoxes), regarding the qi of the months, at the midpoint of the second month, the first Qi ends and transitions into the second Qi; at the midpoint of the eighth month, the fourth Qi ends and transitions into the fifth Qi. However, regarding the qi of the four seasons, it signifies that the qi of yin-yang, cold and warmth, reaches a point where they can be divided equally. Day and night each consist of fifty ke (time units), representing the equal division of yin and yang. Thus, the Classics say: "At the Equinox, the qi differs." When winter and summer mention "Zhi" (Solstices), regarding the Six Qi, at the midpoint of the fifth month, the Si Tian (ruling qi above) reaches its position; at the midpoint of the eleventh month, the Zai Quan (governing qi below) reaches its position. Regarding the commands of the four seasons, it signifies that the qi of yin and yang reaches its extreme limit at this time. At the Summer Solstice, the day does not exceed sixty ke, as yang qi reaches its extremity here; at the Winter Solstice, the day does not fall short of forty ke, as yin qi reaches its extremity here. These represent the state before the heavenly climate changes. Thus, the Classics say: "At the Solstice, the qi is identical."

The Heaven rotates from west to east, while the sun, moon, and five planets revolve around the heaven from east to west. Therefore, the *Baihu Tongyi* states: "Heaven rotates to the left, while the sun, moon, and stars move to the right." It further states: "The sun is yang, and the moon is yin." Their movements have divisions and records, and their cycles follow specific principles. The sun travels one degree across the sky per day and night; one degree consists of one hundred ke, constituting one day. The moon travels slightly more than thirteen degrees across the sky per day and night. This means that within the course of one degree, it is divided into nineteen parts, with each part yielding seven. (One degree has one hundred ke, divided into nineteen parts, each yielding seven. Each part contains slightly more than five ke; five times seven is slightly more than thirty-five ke. Thus, the moon travels slightly more than thirteen degrees and thirty-five ke across the sky per day and night.) Generally, the moon moves swiftly, completing one revolution around the sky in twenty-seven days. Summing up the thirteen degrees and the seven parts of nineteen, it totals twenty-nine days, during which the moon travels slightly more than three hundred eighty-seven degrees across the sky. Comparing the swift motion of the moon to the slow motion of the sun: in twenty-nine days, the sun has only traveled twenty-nine degrees across the sky, whereas the moon has already completed one full revolution, traveling three hundred sixty-five degrees, plus an additional twenty-two degrees across the sky. Consequently, the moon lags behind the sun by seven degrees and has not yet caught up. Proponents of Yin-Yang astrology argue that the movements of the sun and moon naturally have front and back positions, with unequal speeds, lacking a fixed standard, hence the differences between large months and small months. The base should be three hundred sixty-five and one-quarter days, i.e., twenty-five ke. (This implies the sun travels three hundred sixty-five days and twenty-five ke, which constitutes one year.) Excluding the whole year, the remainder is three hundred sixty days; subtracting the six days missing from small months, only three hundred fifty-four days remain to form a year. This results in a total deficit of eleven days and twenty-five ke. Therefore, the system of twelve months is established through intercalation (leap months), giving rise to the Qi of starting the year. A Qi is the culmination of three Hou. At the half-month mark, the direction of the Dipper's handle indicates the direction of the Twelve Earthly Branches. For leap months, there is no establishment of Qi or directional markers; they belong to other Qis but are manifested through the eight solar terms according to the calendar. By calculating the remainder, the leap month is formed, and the degrees of the heaven are completed. Thus, the Classics say: "Establish the origin at the beginning, set the standard in the middle, calculate the remainder at the end, and the degrees of the heaven are complete." This is what is meant.

Observing the profound darkness of the sky, are there still degrees? They use the daily position of the sun and moon, pointing to the Twenty-Eight Mansions (Lunar Lodges) as evidence, and record them as degrees. Thus, the Classics say: "Stars and constellations are used to regulate the movement of the sun and moon." "Regulate" means to establish a system or standard. Heaven also has no "Hou," but uses phenomena such as wind, rain, frost, dew, and vegetation responding to their seasons, which can be verified and predicted, called "Hou." One Hou lasts five days, during which the Five Yuns generate each other and take effect. Like a circle without an end, it cycles repeatedly. The *Book of Documents* states: "A cycle of three hundred sixty-six days, using leap months to determine the four seasons and form the year," which embodies this principle. Physicians must not fail to understand this. The Classics say: "If one does not know the influence added by the year, the flourishing and declining states of the qi, and the origins of deficiency and excess, one cannot serve as a physician."