五行用事 Wuxing Year Cycle
神樞經曰五行旺各有時惟土居無所定乃於四立之前各旺一十八日○
歷例曰立春木立夏火立秋金立冬水各旺七十二日土於四立之前各旺一十八日合之亦為七十二日總三百有六十而歲成矣
The Shenshu Jing states that each of the Wuxing has its own period of dominance, except for ㊏EARTH, which has no fixed position. Instead, Earth becomes dominant for 18 days before each of the four seasonal transitions (Spring Commences / Summer Commences / Autumn Commences / Winter Commences).
The Lili (Calendar Records) explains: ㊍WOOD dominates for 72 days after 315立春Spring-Commences, ㊋FIRE dominates for 72 days after 045立夏Summer-Commences, Autumn Commences — ㊎METAL dominates for 72 days after 135立秋Autumn-Commences, ㊌WATER dominates for 72 days after 225立冬Winter-Commences, ㊏EARTH, however, asserts dominance for 18 days before each of these Commences, totaling 72 days across the year.
When summed, this totals 360 days, forming a complete annual cycle. The system illustrates how the phases and their transitions harmonize with seasonal changes, ensuring the balance and continuity of natural cycles throughout the year.