Dongzhi 冬至 — Winter Solstice

The shortest day — the sun's southernmost point, and traditionally the most important of the twenty-four. Dongzhi falls around 21 December. It is one of the four cardinal terms and, in the classical scheme, the point at which yang begins to return.

It is a solar term — a date fixed by the sun's position, not by the moon. The shortest day — the sun's southernmost point, and traditionally the most important of the twenty-four. Dongzhi is the term where the astronomical, cosmological and customary layers all align, and it is the one the classical sources treat as structurally the most important of the twenty-four.

The classical statement is that the solstice is the turning point rather than the depth: yin reaches its extreme and yang begins in the same moment. Historically it was treated as a festival of the first rank — the saying is that the solstice is as significant as the new year. It is grouped under Water (水) in the five-element system.