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When Qi is in excess, it follows the time of Xiantian (Prior Heaven) to undergo transformation and movement; when Qi is deficient, it follows the time of Houtian (Posterior Heaven) to undergo transformation and movement.
The transformation should be distinguished with precision, regarding the precedence or sequence of Qi movement. Deficiency in Yun (Five Movements) follows Houtian timing, while Excess leads with Xiantian timing.

Sheng (Overcoming) and Fu (Rebounding) occur together in years of deficiency. When Yun declines, the element that overcomes it will inevitably cause pathology. If the Mother element is overcome by its enemy, the Son element, being prosperous, will rebound. The Son's transformation follows the season and may overcome the Mother instead. For example, in a Ding year, Wood Yun is deficient; Metal Qi's clear transformation overcomes it, so the Son Fire Qi rebounds, overcoming Metal with heat transformation. The rest follow this pattern.

Sitan (Heavenly Ruler), Zaiquan (Earthly Ruler), and the four intermediate Qi each govern 60 days and 87.5 ke. Guest Qi executes Heavenly commands and resides above Host Qi, resulting in different transformations such as warmth and coolness, cold and heat, day and night, brightness and darkness, wind and rain, frost and snow, lightning and hail, thunder and lightning. Can the normal seasonal commands of Spring Warmth, Summer Heat, Autumn Coolness, and Winter Cold be entirely deprived by Yun and Qi? No, there are subtle or significant variations at their respective times. Arranging these 60-day Guest Qi under the Host positions allows one to grasp the general method of knowing where the Qi resides.
Regarding Tianfu (Heavenly符), Suihui (Year Meeting), Pingqi (Balanced Qi), and the favorable/unfavorable relationship of Stems and Branches, the mutual generation and restriction between Qi and Yun, Guest overcoming Host, disaster zones, the sequence of time transitions, excessive overcoming and depression rebounding, auspicious signs and disasters, all differ. However, when the Six Qi reach extremity, they become hyperactive, and disasters arise. Thus, when Qi reaches extremity, it reverses; therefore, the Qi that supports it resides below to restrain it, as stated in the classics: "Below Ministerial Fire, Water Qi supports it." There is also Zhongjian Qi (Intermediate Revealing Qi) following it, as stated: "Above Shaoyang, Fire Qi governs, with Jueyin as the Intermediate Revealing Qi." Generally, when Yang reaches extremity, Yin is born; when Yin reaches extremity, Yang is born. This is the wonderful function of the mutual assistance of the Five Elements. The Zhongjian Qi refers to the transformation of mutual overcoming among the six pairs of Hand-Foot meridians and Zang-Fu organs. In heaven and earth, Qi naturally responds.

The Qi of the Five Elements and Yin-Yang distributes across the eight directions. Heavenly Qi descends, Earthly Qi ascends; Earthly Qi is static and constant, while Heavenly Qi is dynamic and changing. The source of the Six Qi is the same, but their sequences differ. Why? Because Heavenly Qi begins with Shaoyin (Ministerial Fire) and ends with Jueyin (Wind-Wood). The classics say: "Shaoyin is called the Mark, Jueyin is called the End." Earthly Qi begins with Jueyin (Wind-Wood) and ends with Taiyang (Cold-Water). The classics say: "To the right of the Bright Manifestation is the position of Sovereign Fire."
Thus, the Six Primal Qi of Heaven correspond inversely to the Twelve Earthly Branches of Earth, using the proper and counter transformations of the Five Elements as their sequence. Shaoyin governs Zi and Wu years, Taiyin governs Chou and Wei years, Shaoyang governs Yin and Shen years, Yangming governs Mao and You years, Taiyang governs Chen and Xu years, and Jueyin governs Si and Hai years. Such is the reason for the beginning and end of Heavenly Qi.
The Six Qi of Earth correspond inversely to the Four Seasons of Heaven, with Wind, Heat, Summer Heat, Dampness, Dryness, and Cold as their sequence. Jueyin Wind-Wood governs Spring, Shaoyin Sovereign Fire governs late Spring and early Summer, Shaoyang Ministerial Fire governs Summer, Taiyin Damp-Earth governs Late Summer, Yangming Dry-Metal governs Autumn, and Taiyang Cold-Water governs Winter. Such is the reason for the beginning and end of Earthly Qi.
The classics say: "Heaven has Yin and Yang, and Earth also has Yin and Yang," referring to the mutual approach of upper and lower. Heavenly Qi moves and does not cease, thus shifting right every five years. Earthly Qi is static and holds its position. Heavenly Qi does not add to Sovereign Fire, so after five years, one Qi remains, shifting right above Ministerial Fire, because Sovereign Fire does not stand alone as a year. The cycle of Earth lasts five years for one revolution, while the cycle of Heaven lasts six periods for completion. A five-year cycle means the Qi of the Five Elements pervades; a six-period completion means the positions of the Six Qi are complete. This is slightly similar to the sequence of Stem adding to Branch, taking the interlacing of Yin and Yang and the mutual multiplication of upper and lower to complete the meaning of the cycle. By combining five and six, thirty years constitute one Ji (cycle), making sixty years.