金光明經文句記 6.36

6.36

Second, explaining the exposition in pairs of two, which has three parts: first, relying on secular methods. Earth lodged in the four seasonal months refers to the third, sixth, ninth, and twelfth months. Each having eighteen days refers to the four seasonal months together totaling seventy-two days. Being merely the two months of yin and yang means that odd numbers are taken as yang and even numbers as yin. As for yang earth and yin earth, because the one yang arises from the winter solstice, proceeding in the yang cycle, the twelfth and third months are yang earth. Because the one yin arises from the summer solstice, proceeding in the yin cycle, the sixth and ninth months are yin earth. From "if discussed" downward, the two yang earths and two yin earths also form pairs of two; thus adding their base months completes the full six seasons.