《周书·本纪·卷三》
到了孔子时，他考察阴阳变化，说正值实行夏历的时候，为后世君王所不改变。
逮于尼父，稽诸阴阳，云行夏之时，后王所不易。
When Confucius came to power, he examined the changes in yin and yang and said that it was the right time to implement the Xia calendar, which has not been changed by later kings.