Library

Set the first day of the first month in the Jiazi year of the first year of Linde era of the Great Tang as a Jiyou day (new moon). From then until the Gui Chou year of the fourth year of Mingchang era, a total of five hundred and thirty years have accumulated. Subtract one calculation from this number, and multiply by the solar year cycle (one year equals 365.25 degrees), specifically three hundred sixty-five degrees, twenty-four fen, and thirty-six seconds. The product is nine hundred thirty-two million one hundred thirty-eight thousand six hundred forty-four fen. Subtract the difference for the Jiao Si day (the moment of solar term transition), which is one hundred forty-six thousand one hundred nine. After removing multiples of sixty (the sexagenary cycle) based on the Tian Ji method, there remain fifty-nine days, two thousand five hundred forty-three fen, and one second. Assigning this to the Jiyou day, the Da Yu (major remainder) corresponds to the Wushen day. This occurs around the time of Dahan (Great Cold) and the equinoxes, indicating that the transition happens before or after Dahan, or precisely on the day of Dahan.

Starting with the Da Yu of the Dahan Jiao Si day, which is fifty-nine days, add the Yun Ce (period of operation, here specified as seventy-three days).

For the second Yun (operation period), cumulatively add the Yun Ce. When it reaches sixty, discard it (as it completes a cycle). By assigning it to the Jiyou day, one can observe the Gan-Zhi (Heavenly Stems and Earthly Branches) of the day and hour when the Yun transitions, thereby distinguishing them clearly.

For each Yun, take the Xiao Yu (minor remainder in fen), divide by six, and multiply by five hundred. Divide this into sixty parts corresponding to one Chen (two-hour period), forming one Ke (a unit of time, here equivalent to 15 minutes in modern terms or a specific fractional unit). Assign this to the start of Zi (midnight). After calculation, the specific time is obtained; for example, Si Zheng (mid-Si hour) at four Ke.

For instance, let the Xiao Yu for Dahan be two thousand five hundred forty-three fen. Shift the decimal point one place to the left to get two hundred fifty-four fen. Multiply by six to obtain one thousand five hundred twenty-four fen. One thousand fen corresponds to five Chen (hours). From the remaining five hundred fen, subtract two hundred fifty, which constitutes half a Chen. If there is a half-Chen remainder, it is designated as "Zheng" (exact); if not, it is "Chu" (initial). Additionally, there are more than two hundred fifty fen, plus twenty-five fen, totaling two hundred seventy-five fen. Sixty fen make one Ke. Subtract two hundred forty fen, leaving four Ke. The remaining thirty-five fen are discarded. Counting from Zi, five Chen lands on Si. Since there is a half-Chen remainder, it is Si Zheng at four Ke.

The East belongs to Wood, which is Jueyin Wind-Wood. This marks the beginning of the commands of Heaven and Earth. In Spring, Wood Qi is prosperous; Jueyin governs the Sky as the primary transforming Qi, causing Spring Wind to prevail. Jueyin governs the Sky as the primary opposing Qi. In Summer, Fire Qi is prosperous; Shaoyin governs the Sky as the primary transforming Qi, causing Summer Heat to prevail. Shaoyin governs the Sky as the primary opposing Qi. In the transitional seasons (Late Summer/Earth), Earth Qi is prosperous; Taiyin governs the Sky as the primary transforming Qi, causing Dampness to prevail. Taiyin governs the Sky as the primary opposing Qi. In Autumn, Metal Qi is prosperous; Yangming governs the Sky as the primary transforming Qi, causing Autumn Dryness to prevail. Yangming governs the Sky as the primary opposing Qi. In Winter, Water Qi is prosperous; Taiyang governs the Sky as the primary transforming Qi, causing Winter Cold to prevail. Taiyang governs the Sky as the primary opposing Qi. Heaven and Earth, above and below, ascending and descending, Yin and Yang combine. The primordial true Qi of Taiyi within Heaven and Earth differentiates into two, becoming Yin and Yang, and arranges into six. In Heaven, these manifest as Cold, Heat, Dryness, Dampness, Wind, and Fire, received by the Three Yin and Three Yang. On Earth, they correspond to Wood, Fire, Earth, Metal, and Water, responding downward through Growth, Transformation, and Storage. Understanding this allows one to comprehend the principles. Heaven and Earth each possess Three Yin and Three Yang; the Sages measured this and established the Twelve Earthly Branches.