《汉书·志·天文志》
阳气盛，太阳逐渐推移向北，白天逐渐长，阳胜，天气为温暑；阴气盛，则太阳逐渐退向南，白天渐短，阴胜，天气寒冷。
阳用事则日进而北，昼进而长，阳胜，故为温暑；阴用事则日退而南，昼退而短，阴胜，故为凉寒也。
When the yang energy is strong, the sun gradually moves northward, the day gradually becomes longer, yang wins, and the weather is warm and hot; when the yin energy is strong, the sun gradually retreats southward, the day gradually becomes shorter, yin wins, and the weather is cold.