此太古占天之始，察五气，纪五天，而所立五运也。五天五气者，谓望气之时，见丹天之火气，经于牛女
璧奎四宿之上，下临戊癸之方，此戊癸之所以为火运也。 天之土气，经于心尾角轸四宿之上，下临甲己之方，
此甲己之所以为土运也。苍天之木气，经于危室柳鬼四宿之上，下临丁壬之方，此丁壬之所以为木运也。素天
之金气，经于亢氐昴毕四宿之上，下临乙庚之方，此乙庚之所以为金运也。元天之水气，经于张翼娄胃四宿之
上，下临丙辛之方，此丙辛之所以为水运也。是知五运之化，莫不有所由从，盖已肇于开辟之初矣。详《太史天
元册文》，及《天元纪大论》中。
自太始初分，阴阳析位，虽五运之象，昭于五天，然尚有月建之法，及十二肖之说，则立运之法，因是又
一理。
月建者，单举正月为法。如甲己之岁，正月首建丙寅，丙者火之阳，火生土，故甲己为土运；乙庚之岁，
正月首建戊寅，戊者土之阳，土生金，故乙庚为金运；丙辛之岁，正月首建庚寅，庚者金之阳，金生水，故丙
辛为水运，丁壬之岁，正月首建壬寅，壬者水之阳，水生木，故丁壬为木运；戊癸之岁，正月首建甲寅，
甲者木之阳，木生火，故戊癸为火运。此五运生于正月之建者也。
十二肖者，谓十二宫中，惟龙善变，而属辰位，凡十干起甲，但至辰宫，即随其所遇之干，而与之俱变矣。
如甲己干头，起于甲子，至辰属戊，戊为土，此甲己之所以化土也；乙庚干头，起于丙子，至辰属庚，庚为金，
此乙庚之所以化金也；丙辛干头，起于戊子，至辰属壬，壬为水，此丙辛之所以化水也；丁壬干头，起于庚子，
至辰属甲，甲为木，此丁壬之所以化木也；戊癸干头，起于壬子，至辰属丙，丙为火，此戊癸之所以化火也。
此又五运之遇龙而变者也。
又一说谓甲刚木，克己柔土为夫妇，而成土运；乙柔木，嫁庚刚金，而成金运；丁阴火，配壬阳水，而成
木运；丙阳火，娶辛柔金，而成水运；戊阳土，娶癸阴水，而成火运。
此三说者，义各不同，今并存之，以备参校。
这是上古时代观测天象的开端，通过考察五气、记录五天，从而确立了五运。所谓五天五气，是指在望气之时，看见丹天的火气，运行经过牛宿、女宿、璧宿、奎宿这四宿之上，向下覆盖戊癸的方向，这就是戊癸之所以成为火运的原因。天的土气，运行经过心宿、尾宿、角宿、轸宿这四宿之上，向下覆盖甲己的方向，这就是甲己之所以成为土运的原因。苍天的木气，运行经过危宿、室宿、柳宿、鬼宿这四宿之上，向下覆盖丁壬的方向，这就是丁壬之所以成为木运的原因。素天的金气，运行经过亢宿、氐宿、昴宿、毕宿这四宿之上，向下覆盖乙庚的方向，这就是乙庚之所以成为金运的原因。元天的水气，运行经过张宿、翼宿、娄宿、胃宿这四宿之上，向下覆盖丙辛的方向，这就是丙辛之所以成为水运的原因。由此可知，五运的变化，无不有所遵循，大概已经始于天地开辟之初了。详见《太史天元册文》及《天元纪大论》中。
自从太始之初，阴阳分离定位，虽然五运的景象昭示于五天之中，然而还有月建的方法，以及十二肖的说法，那么确立运法的原则，因此又有了另一种道理。
月建的方法，单独以正月为例。如在甲己之年，正月的首建是丙寅，丙属于火的阳，火生土，所以甲己为土运；在乙庚之年，正月的首建是戊寅，戊属于土的阳，土生金，所以乙庚为金运；在丙辛之年，正月的首建是庚寅，庚属于金的阳，金生水，所以丙辛为水运；在丁壬之年，正月的首建是壬寅，壬属于水的阳，水生木，所以丁壬为木运；在戊癸之年，正月的首建是甲寅，甲属于木的阳，木生火，所以戊癸为火运。这是五运生于正月月建的结果。
十二肖的说法，是指十二宫之中，只有龙善于变化，且归属于辰位，凡是十天干起于甲，只要到达辰宫，就随着它所遇到的天干，而与之一起变化了。如甲己干头，起于甲子，到辰时属戊，戊为土，这就是甲己之所以化为土的原因；乙庚干头，起于丙子，到辰时属庚，庚为金，这就是乙庚之所以化为金的原因；丙辛干头，起于戊子，到辰时属壬，壬为水，这就是丙辛之所以化为水的原因；丁壬干头，起于庚子，到辰时属甲，甲为木，这就是丁壬之所以化为木的原因；戊癸干头，起于壬子，到辰时属丙，丙为火，这就是戊癸之所以化为火的原因。这又是五运遇到龙而发生变化的情况。
又有一种说法认为，甲是刚木，克制己柔土，如同夫妇关系，从而形成土运；乙是柔木，嫁给庚刚金，从而形成金运；丁是阴火，配合壬阳水，从而形成木运；丙是阳火，娶辛柔金，从而形成水运；戊是阳土，娶癸阴水，从而形成火运。
这三种说法，义理各不相同，现在并存它们，以备参考校对。
This marks the beginning of celestial observation in ancient times, where by examining the Five Qi (Five Phases' energetic manifestations) and recording the Five Days (specific celestial configurations), the system of Wu Yun (Five Movements/Phases) was established. The concept of "Five Days and Five Qi" refers to the phenomenon observed during qi-gazing: the Fire Qi (Huo Qi) of Dan Tian (Red Heaven) traverses above the four lunar mansions—Niu (Ox), Nü (Girl), Bi (Wall), and Kui (Legs). It descends to cover the directions associated with Wu and Gui; this is why Wu and Gui correspond to the Fire Movement. The Earth Qi (Tu Qi) of Heaven traverses above Xin (Heart), Wei (Tail), Jiao (Horn), and Zhen (Screen) mansions, descending to cover the directions of Jia and Ji; this is why Jia and Ji correspond to the Earth Movement. The Wood Qi (Mu Qi) of Cang Tian (Azure Heaven) traverses above Wei (Danger), Shi (Room), Liu (Willow), and Gui (Ghost) mansions, descending to cover the directions of Ding and Ren; this is why Ding and Ren correspond to the Wood Movement. The Metal Qi (Jin Qi) of Su Tian (White Heaven) traverses above Kang (Neck), Di (Root), Mao (Bright), and Bi (Net) mansions, descending to cover the directions of Yi and Geng; this is why Yi and Geng correspond to the Metal Movement. The Water Qi (Shui Qi) of Yuan Tian (Black Heaven) traverses above Zhang (Net), Yi (Wings), Lou (Stomach), and Wei (Stomach) mansions, descending to cover the directions of Bing and Xin; this is why Bing and Xin correspond to the Water Movement. From this, it is known that the transformations of the Five Movements have their origins, likely dating back to the initial creation of heaven and earth. For details, refer to *Taishi Tianyuan Ce Wen* and *Tianyuan Ji Da Lun*.
Since the beginning of Taishi (Great Beginning), when Yin and Yang separated and took their positions, although the imagery of the Five Movements was manifest in the Five Days, there existed also the method of Yue Jian (Monthly Establishment) and the theory of the Twelve Xiao (Zodiac Animals). Thus, the principles for establishing the Movements had another layer of logic.
The method of Yue Jian takes the first month as an example. In years governed by Jia and Ji, the first month begins with Bing Yin. Bing represents the Yang aspect of Fire; since Fire generates Earth, Jia and Ji correspond to the Earth Movement. In years governed by Yi and Geng, the first month begins with Wu Yin. Wu represents the Yang aspect of Earth; since Earth generates Metal, Yi and Geng correspond to the Metal Movement. In years governed by Bing and Xin, the first month begins with Geng Yin. Geng represents the Yang aspect of Metal; since Metal generates Water, Bing and Xin correspond to the Water Movement. In years governed by Ding and Ren, the first month begins with Ren Yin. Ren represents the Yang aspect of Water; since Water generates Wood, Ding and Ren correspond to the Wood Movement. In years governed by Wu and Gui, the first month begins with Jia Yin. Jia represents the Yang aspect of Wood; since Wood generates Fire, Wu and Gui correspond to the Fire Movement. These are the Five Movements derived from the establishment of the first month.
The theory of the Twelve Xiao states that among the twelve palaces, only the Dragon (Chen) possesses transformative powers and is associated with the Chen position. Whenever the Ten Heavenly Stems begin with Jia, upon reaching the Chen palace, they transform according to the stem encountered there. For instance, starting from Jia Zi for the Jia/Ji cycle, upon reaching Chen, it becomes Wu; since Wu is Earth, Jia and Ji transform into Earth. Starting from Bing Zi for the Yi/Geng cycle, upon reaching Chen, it becomes Geng; since Geng is Metal, Yi and Geng transform into Metal. Starting from Wu Zi for the Bing/Xin cycle, upon reaching Chen, it becomes Ren; since Ren is Water, Bing and Xin transform into Water. Starting from Geng Zi for the Ding/Ren cycle, upon reaching Chen, it becomes Jia; since Jia is Wood, Ding and Ren transform into Wood. Starting from Ren Zi for the Wu/Gui cycle, upon reaching Chen, it becomes Bing; since Bing is Fire, Wu and Gui transform into Fire. This describes how the Five Movements change upon encountering the Dragon.
Another interpretation suggests that Jia (Yang Wood) controls Ji (Yin Earth), forming a marital relationship that results in the Earth Movement; Yi (Yin Wood) marries Geng (Yang Metal), resulting in the Metal Movement; Ding (Yin Fire) pairs with Ren (Yang Water), resulting in the Wood Movement; Bing (Yang Fire) marries Xin (Yin Metal), resulting in the Water Movement; Wu (Yang Earth) marries Gui (Yin Water), resulting in the Fire Movement.
These three theories differ in their reasoning. They are preserved here together for reference and comparison.