治时令之病，宜乎先究运气。经曰∶“不知年之所加，气之盛衰，不可以为工也。”戴人云∶“不读
五运六气，检遍方书何济。”由是观之，治时病者，可不知运气乎！近世之医，皆谓五运六气，与岁多有不
应，置之弗习，是未达夫天地之常变也。常者如君相司令则当热，寒水主政则当寒，变者当热反寒，当
寒反热之类是也。试以其常而言之，五运者，木、火、土、金、水也，一运主七十二日有奇。六气者，风、
君、相、湿、燥、寒也，一气司六十日有奇。故五运六气合行，而终一岁。盖主运主气，岁岁皆然；客运
客气，年年更换。每年从大寒日，初交木运，二为火运，三为土运，四为金运，终为水运，此主运也。经曰∶
“甲己之岁，土运统之；乙庚之岁，金运统之；丙辛之岁，水运统之；丁壬之岁，木运统之；戊癸之岁，
火运统之。”如甲己之年，甲己化土，土为初运，金为二运，水为三运，木为四运，火为五
运，此客运也。主气亦从大寒日交，厥阴风木为初气，少阴君火为二气，少阳相火为三气，太阴湿土为四气，
阳明燥金为五气，太阳寒水为终气，此主气也。客气每岁循环，根据年推算，如子午之年，初为寒水，二为
风木，三为君火，四为湿土，五为相火，终为燥金。又如丑未，初为风木；寅申，初为君火；卯酉，初
为湿土，辰戌，初为相火；巳亥，初为燥金，此客气也。每年三气为司天，终气为在泉。如子午之年，三气
是君火，乃君火司天，主热淫所胜。终气是燥金，乃燥金在泉，主燥淫于内。其余可类推矣。倘遇壬、戊、
甲、庚、丙之年，皆曰太过，木曰发生，火曰赫曦，土曰敦阜，金曰坚成，水曰流衍。丁、癸、己、乙、
辛之年，皆曰不及，木曰委和，火曰伏明，土曰卑监，金曰从革，水曰涸流。若太过被克，不及得助，皆曰
平运，木曰敷和，火曰
升明，土曰备化，金曰审平，水曰静顺。此述五运六气之主客，司天在泉，太过不及之大概。在学人，先宜
熟此有定之常，然后审其无定之变可也。倘欲深求底蕴，再考《内经》，慎毋惑于飞畴运气不足凭之说耳。
治疗时令疾病，应当首先探究五运六气的变化规律。《内经》说：“不知道当年干支所加临的运气情况，以及气机的盛衰变化，就不能成为合格的医生。”戴人（张从正）说：“如果不研读五运六气，即使翻遍所有医书又有什么用处呢？”由此看来，治疗时病的人，怎么能不了解运气理论呢！近世的医生，都声称五运六气与实际情况往往不相符合，因此将其搁置而不学习，这是没有通达天地运行的常规与变通规律。所谓“常”，是指当令之气应有的正常状态，如君火、相火当令则天气应当热，寒水主政则天气应当寒；所谓“变”，是指应当热的时候反而寒冷，应当冷的时候反而炎热等情况。
试着从“常”的角度来说，五运，即木、火、土、金、水五行之运，每一运主管七十二天多一点的时间。六气，即风、君火、相火、湿、燥、寒六种气候特征，每一气主管六十天多一点的时间。所以五运和六气配合运行，完成一年的周期。其中，主运和主气，每年都是固定的；而客运和客气，每年都发生变化。每年从大寒日开始，初次交接的是木运，第二次是火运，第三次是土运，第四次是金运，最后是 water 运，这叫做主运。《内经》说：“甲年和己年，由土运统领；乙年和庚年，由金运统领；丙年和辛年，由水运统领；丁年和壬年，由木运统领；戊年和癸年，由火运统领。”例如在甲年或己年，天干甲己化土，土为初运，金为二运，水为三运，木为四运，火为五运，这叫做客运。
主气也从大寒日开始交接，厥阴风木为初气，少阴君火为二气，少阳相火为三气，太阴湿土为四气，阳明燥金为五气，太阳寒水为终气，这叫做主气。客气每年循环变化，根据年份推算，例如子年和午年，初气为寒水，二气为风木，三气为君火，四气为湿土，五气为相火，终气为燥金。又如丑年和未年，初气为风木；寅年和申年，初气为君火；卯年和酉年，初气为湿土；辰年和戌年，初气为相火；巳年和亥年，初气为燥金，这叫做客气。每年的第三气称为司天，终气称为在泉。例如子年和午年，第三气是君火，即是君火司天，主管热气过度盛行。终气是燥金，即是燥金在泉，主管燥气内盛。其余年份可以类推。
如果遇到壬、戊、甲、庚、丙之年，都称为“太过”。木运太过称为“发生”，火运太过称为“赫曦”，土运太过称为“敦阜”，金运太过称为“坚成”，水运太过称为“流衍”。遇到丁、癸、己、乙、辛之年，都称为“不及”。木运不及称为“委和”，火运不及称为“伏明”，土运不及称为“卑监”，金运不及称为“从革”，水运不及称为“涸流”。如果太过之气被克制，或者不及之气得到相助，都称为“平运”。木运平运称为“敷和”，火运平运称为“升明”，土运平运称为“备化”，金运平运称为“审平”，水运平运称为“静顺”。以上叙述了五运六气中主运与客气、司天与在泉、太过与不及的大概情况。对于学习者来说，应当先熟记这些有定数的常规，然后再审视那些无定数的变化即可。如果想要深入探究其根本原理，再查阅《内经》，千万不要被那些认为飞畴（指古代术数推演）运气之说不足凭信的观点所迷惑。
To treat diseases of the seasonal climate, one should first investigate the principles of Wu Yun Liu Qi (Five Movements and Six Qi). The Classic states: "One who does not know the annual stem-branch influences, nor the prosperity and decline of the Qi, cannot be considered a qualified physician." Dai Ren (Zhang Congzheng) said: "Without studying Wu Yun Liu Qi (Five Movements and Six Qi), what is the use of consulting all medical books?" From this, it can be seen that those treating seasonal diseases must understand the theory of Yun Qi (Luck and Qi)! Physicians in recent times often claim that Wu Yun Liu Qi (Five Movements and Six Qi) rarely corresponds with actual conditions, so they neglect it and do not study it. This demonstrates a failure to comprehend the constant changes of Heaven and Earth. The "constant" refers to the normal state where, for instance, when Jun Huo (Minister Fire) and Xiang Huo (Ministerial Fire) are in command, the weather should be hot; when Han Shui (Cold Water) governs, the weather should be cold. The "variable" refers to situations such as it being hot when it should be cold, or cold when it should be hot.
Speaking from the perspective of the "constant": Wu Yun (Five Movements) consists of Wood, Fire, Earth, Metal, and Water. Each Movement governs slightly more than seventy-two days. Liu Qi (Six Qi) consists of Wind, Jun Huo (Minister Fire), Xiang Huo (Ministerial Fire), Dampness, Dryness, and Cold. Each Qi governs slightly more than sixty days. Thus, Wu Yun (Five Movements) and Liu Qi (Six Qi) combine to complete one year. The Zhu Yun (Principal Movement) and Zhu Qi (Principal Qi) remain the same every year; whereas the Ke Yun (Passing Movement) and Ke Qi (Passing Qi) change annually. Every year, starting from the Great Cold solar term, the first interaction is Wood Yun (Movement), followed by Fire Yun (Movement), then Earth Yun (Movement), then Metal Yun (Movement), and finally Water Yun (Movement); this is called Zhu Yun (Principal Movement). The Classic states: "In years of Jia and Ji, Earth Yun (Earth Movement) governs; in years of Yi and Geng, Metal Yun (Metal Movement) governs; in years of Bing and Xin, Water Yun (Water Movement) governs; in years of Ding and Ren, Wood Yun (Wood Movement) governs; in years of Wu and Gui, Fire Yun (Fire Movement) governs." For example, in Jia or Ji years, Jia and Ji transform into Earth, making Earth the first movement, Metal the second, Water the third, Wood the fourth, and Fire the fifth; this is called Ke Yun (Passing Movement).
Zhu Qi (Principal Qi) also begins at the Great Cold solar term: Jue Yin Feng Mu (Jueyin Wind-Wood) is the first Qi, Shao Yin Jun Huo (Shaoyin Minister Fire) is the second Qi, Shao Yang Xiang Huo (Shaoyang Ministerial Fire) is the third Qi, Tai Yin Shi Tu (Taiyin Damp-Earth) is the fourth Qi, Yang Ming Zao Jin (Yangming Dryness-Metal) is the fifth Qi, and Tai Yang Han Shui (Taiyang Cold-Water) is the final Qi; this is called Zhu Qi (Principal Qi). Ke Qi (Passing Qi) cycles annually and is calculated based on the year. For instance, in Zi and Wu years, the first Qi is Cold Water, the second is Wind Wood, the third is Minister Fire, the fourth is Damp Earth, the fifth is Ministerial Fire, and the final Qi is Dryness Metal. Similarly, in Chou and Wei years, the first Qi is Wind Wood; in Yin and Shen years, the first Qi is Minister Fire; in Mao and You years, the first Qi is Damp Earth; in Chen and Xu years, the first Qi is Ministerial Fire; in Si and Hai years, the first Qi is Dryness Metal; this is called Ke Qi (Passing Qi). The third Qi of each year is called Si Tian (Heavenly Command), and the final Qi is called Zai Quan (Earthly Spring). For example, in Zi and Wu years, the third Qi is Minister Fire, meaning Minister Fire commands Heaven, governing excessive heat. The final Qi is Dryness Metal, meaning Dryness Metal commands Earth, governing internal dryness. The rest can be inferred similarly.
If encountering years of Ren, Wu, Jia, Geng, or Bing, these are termed "Excessive" (Tai Guo). Wood Excessive is called Fa Sheng (Sprouting), Fire Excessive is called He Xi (Blazing), Earth Excessive is called Dun Fu (Mounding), Metal Excessive is called Jian Cheng (Hardening), and Water Excessive is called Liu Yan (Overflowing). If encountering years of Ding, Gui, Ji, Yi, or Xin, these are termed "Deficient" (Bu Ji). Wood Deficient is called Wei He (Withered Harmony), Fire Deficient is called Fu Ming (Hidden Brightness), Earth Deficient is called Bei Jian (Low Supervision), Metal Deficient is called Cong Ge (Following Reform), and Water Deficient is called He Liu (Dried Flow). If an Excessive Qi is controlled, or a Deficient Qi receives assistance, these are termed "Balanced Movement" (Ping Yun). Wood Balanced is called Fu He (Spreading Harmony), Fire Balanced is called Sheng Ming (Ascending Brightness), Earth Balanced is called Bei Hua (Complete Transformation), Metal Balanced is called Shen Ping (Judging Peace), and Water Balanced is called Jing Shun (Quiet Obedience). This outlines the general principles of Principal and Passing Movements/Qi, Heavenly Command and Earthly Spring, and Excess and Deficiency within Wu Yun Liu Qi (Five Movements and Six Qi). Students should first familiarize themselves with these fixed constants, and then examine the unfixed variables. If one wishes to delve deeper into the underlying principles, they should consult the *Nei Jing* (Classic of Internal Medicine), and beware of being confused by claims that astronomical calculations and Yun Qi theories are unreliable.