Subtle Discernment Periods

Subtle Discernment Periods (洞微大限) is the longest of the timing layers, the one that divides a life into a handful of chapters rather than years or months. The name is literal: 洞 is to see through, 微 is the fine grain — the layer that discerns the slow shifts a single year is too short to show.

The advancing point begins at the boundary of the Life Palace and moves counter-zodiacally, one palace at a time. Each palace spans the same thirty degrees, but the years allotted to each palace differ — so the point moves at a different rate through each one, and the periods come out markedly unequal in length. This is the defining structural feature: these are not twelve equal chapters.

Within a palace the timeline subdivides again wherever the advancing degree crosses a boundary of the twenty-eight mansions, giving a finer sequence of segments across the circuit. Boundaries are computed from the ephemeris to the degree, so a period change carries a date and a time rather than an approximate year.

The layer is read alongside the natal chart: when the advancing point contacts the longitude of a natal body, that contact marks the period out from those around it.