Chunfen 春分 — Spring Equinox

The equinox — the day of equal light, and the midpoint of spring. Chunfen falls around 20 March. Day and night are of equal length and the sun crosses the equator northward. It is one of the four terms that mark the cardinal points of the solar year.

It is a solar term — a date fixed by the sun's position, not by the moon. The equinox — the day of equal light, and the midpoint of spring. The equinoxes and solstices were observed and measured before the rest of the twenty-four were interpolated, which is why they carry more weight in the classical material.

The four cardinal terms — the two equinoxes and the two solstices — are the ones the classical sources treat as structurally important, and they are the terms that the older calendars are anchored to. It is grouped under Wood (木) in the five-element system.