The 10 Heavenly Stems & 12 Earthly Branches are apportioned between the Yin & Yang principles by equating each odd number with Yang and each even number with Yin. Thus of the Heavenly Stems, chia, ping, wu, keng & jen belong to "Yang," while i, ting, chi, hsin & kuei belong to "Yin."
天干地支配陰陽，規則簡單，只要依據古人的「自由心證」﹘﹘凡是奇數就屬陽、凡是偶數就屬陰，因此天干十位中，甲丙戊庚壬屬「陽」，乙丁己辛癸屬「陰」，地支也是如此。