即三阴三阳。又内六步，每步统四小气，得六十日另八十七
刻半。主气，地气也，静而守位，故四时有常。太阴居少阳后，以岁时为法也。
初之气∶厥阴风木，大寒、立春、雨水、惊蛰。
二之气∶少阴君火，春分、清明、谷雨、立夏。
三之气∶少阳相火，小满、芒种、夏至、小暑。
四之气∶太阴湿土，大暑、立秋、处暑、白露。
五之气∶阳明燥金，秋分、寒露、霜降、立冬。
终之气∶太阳寒水，小雪、大雪、冬至、小寒。
主气逐年皆同，惟以客气临于其际，遂有生克制化之当。
客气，天气也，动而不息，故逐年各异。太阴居少阳前，以阴阳为类从也。每气与主气同，各得六十日另
八十七刻半。
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逐年客气横看加临主气之上，即有生克制化之处，而人身感之，经络受疾之源可知已。
大抵客气最盛，当视以为凭，而主气只以奉天之本令，如春木夏火四令而已，似不必拘，盖以有胜而无复
也。
其起只以司天前二位为初气，在泉为终气，最易明晰。
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子午∶少阴君火司天，阳明燥金在泉。
丑未∶太阴湿土司天，太阳寒水在泉。
寅申∶少阳相火司天，厥阴风木在泉。
卯酉∶阳明燥金司天，少阴君火在泉。
辰戌∶太阳寒水司天，太阴湿土在泉。
巳亥∶厥阴风木司天，少阳相火在泉。
以在上司天言，则面北而命其位，所谓左者西而右者东也。
This refers to the Three Yin and Three Yang (San Yin San Yang). Furthermore, within the six internal steps (the six phases of the Dominant Qi), each step governs four minor solar terms, totaling sixty days and eighty-seven and a half ke (ancient Chinese time units). The Dominant Qi (Zhu Qi) is Earthly Qi; it is static and remains in its fixed position, thus the changes of the four seasons are constant. Taiyin Wet Earth follows Shaoyang Ministerial Fire, following the law of the annual sequence.
First Qi: Jueyin Wind-Wood, corresponding to the solar terms Great Cold, Beginning of Spring, Rain Water, Awakening of Insects.
Second Qi: Shaoyin Sovereign Fire, corresponding to the solar terms Spring Equinox, Pure Brightness, Grain Rain, Beginning of Summer.
Third Qi: Shaoyang Ministerial Fire, corresponding to the solar terms Grain Full, Grain in Ear, Summer Solstice, Minor Heat.
Fourth Qi: Taiyin Wet Earth, corresponding to the solar terms Great Heat, Beginning of Autumn, End of Heat, White Dew.
Fifth Qi: Yangming Dry-Metal, corresponding to the solar terms Autumn Equinox, Cold Dew, Frost Descent, Beginning of Winter.
Final Qi: Taiyang Cold-Water, corresponding to the solar terms Minor Snow, Major Snow, Winter Solstice, Minor Cold.
The Dominant Qi is identical year after year; only when the Migratory Qi (Ke Qi) overlays it do the interactions of generation and restriction occur appropriately.
The Migratory Qi is Heavenly Qi; it is dynamic and ceaseless, thus varying from year to year. Taiyin Wet Earth precedes Shaoyang Ministerial Fire, following the principle of classification by Yin-Yang affinity. Each Qi lasts the same duration as the Dominant Qi, namely sixty days and eighty-seven and a half ke.
Observing the Migratory Qi annually in a horizontal manner, it overlays the Dominant Qi, creating situations of generation and restriction. When the human body is affected by these climatic changes, the meridians become the source of disease, which can be understood thereby.
Generally speaking, the Migratory Qi is most potent and should be taken as the standard; the Dominant Qi merely executes the fundamental commands of Heaven, such as Wood in Spring and Fire in Summer, etc., and perhaps need not be rigidly adhered to, as here there is only excess (Sheng) without retaliation (Fu).
Its commencement begins with the two positions preceding Si Tian (Heavenly Ruler) as the First Qi, and the Zai Quan (Earthly Subordinate) position as the Final Qi, which makes it easiest to clarify.
Years of Zi and Wu: Shaoyin Sovereign Fire rules Si Tian (Heaven), Yangming Dry-Metal rules Zai Quan (Earth).
Years of Chou and Wei: Taiyin Wet Earth rules Si Tian, Taiyang Cold-Water rules Zai Quan.
Years of Yin and Shen: Shaoyang Ministerial Fire rules Si Tian, Jueyin Wind-Wood rules Zai Quan.
Years of Mao and You: Yangming Dry-Metal rules Si Tian, Shaoyin Sovereign Fire rules Zai Quan.
Years of Chen and Xu: Taiyang Cold-Water rules Si Tian, Taiyin Wet Earth rules Zai Quan.
Years of Si and Hai: Jueyin Wind-Wood rules Si Tian, Shaoyang Ministerial Fire rules Zai Quan.
Speaking from the perspective of Si Tian above, one faces North to determine the positions, meaning the left is West and the right is East.