鄒衍的五德終始說（亦即五行說）應用在兩方面。一是朝代的興替；二是四時的更代。《呂氏春秋．應同》論朝代興替即采用鄒衍五行說，這點學者已多十論列，王夢鷗教授論之尤詳。尚待探討的是〈月令〉所載一年四時的更代是否根據鄒衍說。本文從五行四時的關係著手。論者多以為五行與四時直接相配，但原來應是四時與四方，五行則與五方或五位相配。五行與四時的相配是通過五方或五位的，最初相配未能完全整齊劃一，這是顯而易見的。但更重要的是實行並無一致的模式。在土與中央相配的過程中，在〈月令〉裡，土在一年之中不佔任何時間。到了《淮南子．時則》才把夏季最後一個原屬火的六月撥歸土。《淮南子》這個處理辦法似乎和鄒衍說一致。可見〈月令〉在處理五行與四時關係時采取與鄒衍不同的手法。

Tsou Yen's theory of the Cylcle of the Five Virtues ( 五德 ) in other words, the Five Rotatory Ascendants, has two applications. In the first instance, it applies to the succession of dynasties. In the second, it applies to the seasons of the year. That the "Ying-tung" 應同 chapter of the Lu-shih ch'un-ch'iu has incorporated the former application has been shown by previous scholars, particularly Professor Wang Meng-ou 王夢鷗. What remains to be investigated is whether the "Yueh-ling" 月令 represents the latter application. The investigation approaches the problem through the correlation of the Five Ascendants with the Four Seasons, and although it is commonly assumed that they were directly correlated, this paper argues that originally the Four Seasons were correlated with the Four Seasons, and although it is commonly assumed that they were directly correlated, this paper argues that originally the Four Seasons were correlated with the Four Positions (四方) and the Five Ascendants with the Five Positions (五方, 五位). The Five Ascendants were, then, superimposed on to the Four Positions and in turn on to the Four Seasons through the mediation of the Five Positions. This can be seen from the lack of any attempt at integrating the two. For us, what is more important is the lack of uniformity in the practice. T'u (土, earth ) which is correlated with chung-yang (中央, centre) is not given a peroid of time of its own in the "Yueh-ling" whereas in the "Shih-tze" 時則 of the Huai-nan-tzu 淮南子, the last month of summer is taken from huo (火, fire) and given to t'u. There is some evidence Yen advocated. Thus the "Yueh-ling" seems to have followed a method somewhat different from that followed by Tsou Yen in the correlation of the wu hsing with the Four Seasons.