Day Master

What it is

A Four Pillars (Saju / Bazi) chart has eight characters: four pairs of a heavenly stem and an earthly branch, one pair for your birth year, month, day, and hour. Three of those four pillars describe your surroundings — the day pillar describes you. Its stem, called the day master, is the one fixed point the rest of the chart is measured against.

There are ten heavenly stems, and each one carries a yin or yang form of one of the five elements: wood, fire, earth, metal, water. Your day master is whichever of the ten falls on your birth day, and it never changes — it is set by the calendar date alone, the same way a person's sun sign is set by their birth date in Western astrology.

Worked example

Someone born August 5, 1990 has a day pillar of 壬寅 — stem 壬 (Im), water in its yang form. Their day master is Water. Every other stem in their chart is then classified as a ten-god relationship to Water: their year stem 庚 (metal) reads as a "resource" (metal generates water), their month stem 癸 (also water, but yin) reads as a "peer" of the opposite polarity, and, if they were born at 12:00 noon, their hour stem 丙 (fire) — Mystica's engine derives all of this directly from the same lunar-calendar conversion described below — reads as "wealth" (water controls fire). With no birth hour there is no hour stem to read.

How Mystica computes it

The free reading at Saju derives your day stem from the lunar calendar conversion of your exact birth date, then classifies the rest of your eight characters against it using the classical ten-god table. Nothing here is estimated: the day master is fixed by the date alone, which is why the reading needs your exact birth date but — unlike the hour pillar — not strictly the time of day.