当复得甲子。而气盈朔虚。每岁递迁。于是至日不必皆值甲子。当以冬至后六十日花甲
一周。正为雨水之候为正。雨水者。冰雪解散而为雨水。天气温和之始也。云少阳起者。
阳方起而出地。阳始生者。阳始盛而生物。非冬至一阳初生之谓也。窃尝论之矣。夏
至一阴生。而后有小暑大暑。冬至一阳生。而后有小寒大寒。非阴生而反热。阳生而反
寒也。天地之道。否不极则不泰。阴阳之气。剥不极则不复。夏至六阳尽于地上。而后
一阴生于地下。是阴生之时。正阳极之时也。冬至六阴尽于地上。而后一阳生于地下。
是阳生之时。正阴极之时也。阳极而大热。阴极而大寒。自然之道也。则所谓阳始生。
天得温和者。其不得与冬至阳生同论也审矣。至未得甲子而天已温。或已得甲子而天反
未温。及已得甲子而天大寒不解。或如盛夏五六月时。则气之有盈有缩。
为候之或后或先。而人在气交之中者。往往因之而病。惟至人为能与时消息而无忤耳。
One must complete another Jiazi cycle (a 60-day cycle). Due to the surplus of Qi (Qi Ying) and the deficiency of the lunar phases (Shuo Xu), the solar terms shift progressively each year. Consequently, the Winter Solstice does not always coincide with a Jiazi day. The correct timing for the Rain Water (Yushui) solar term should be considered as sixty days after the Winter Solstice, completing one full Jiazi cycle. "Rain Water" refers to the melting of ice and snow into rain, marking the beginning of mild weather. When it is said that "Shaoyang (Lesser Yang) arises," it means Yang Qi is just rising from beneath the earth; when it is said that "Yang begins to generate," it means Yang Qi is beginning to flourish and give birth to things. This is not referring to the initial generation of Yang at the Winter Solstice. I have previously discussed this: At the Summer Solstice, Yin begins to generate, followed by Minor Heat (Xiaoshu) and Major Heat (Dashu); at the Winter Solstice, Yang begins to generate, followed by Minor Cold (Xiaohan) and Major Cold (Dahan). This does not mean that the generation of Yin leads to heat, or the generation of Yang leads to cold. The Way of Heaven and Earth dictates that obstruction (Pi) will not turn into smoothness (Tai) unless it reaches its extreme, and Yin and Yang Qi will not recover unless they are peeled away to their extreme. At the Summer Solstice, the six Yang energies on the ground are exhausted, and then one Yin energy generates beneath the ground. Thus, when Yin generates, it is precisely when Yang is at its extreme. At the Winter Solstice, the six Yin energies on the ground are exhausted, and then one Yang energy generates beneath the ground. Thus, when Yang generates, it is precisely when Yin is at its extreme. Extreme Yang results in intense heat, and extreme Yin results in intense cold; this is the natural Dao. Therefore, the statement that "Yang has just begun to generate, and the sky has become mild" clearly cannot be equated with the generation of Yang at the Winter Solstice. If the weather becomes warm before the Jiazi day arrives, or remains cold despite the Jiazi day having passed, or if severe cold persists even after the Jiazi day, or if it resembles the heat of the fifth and sixth months of midsummer, these indicate that Qi has both surplus and deficit, and climatic conditions may be either delayed or advanced. Humans living within the intersection of Qi often fall ill due to these variations. Only those who have attained perfection can harmonize with the changing seasons without conflict.