The Four Pillars
八字 means “eight characters” — two for each of four pillars: year, month, day and hour. Each pillar pairs a Heavenly Stem (天干) with an Earthly Branch (地支), and together those eight characters describe the elemental weather at the moment you were born.
The Day Master — the Heavenly Stem of your day pillar — represents you. Everything else in the chart is read in relation to it. A chart is not “good” or “bad”; it is balanced or unbalanced, and the work is in knowing which.
Why boundary rules matter
A surprising number of free BaZi calculators are wrong, and always in the same two ways. The first is treating 1 January as the year boundary; the correct boundary is 立春, usually 3–5 February. The second is deriving the month pillar from the calendar month rather than from the 節 solar terms.
This calculator uses the solar-term boundaries and the 五虎遁 and 五鼠遁 derivation rules. If you have used another tool and the pillars differ, check whether you were born in late January or early February — that is almost always where the disagreement comes from.
Element balance and the favourable element
The chart counts not only the visible stems and branches but the hidden stems inside each branch, weighted by season. From that distribution the reading identifies which element your chart lacks or over-carries, and therefore your 喜用神 — the element that brings the chart into balance.
That single character drives most practical feng shui advice you will ever be given: favourable colours, directions, materials, career fields and the timing of major decisions.
Common questions
What if I don’t know my birth time?
Enter noon and read the chart as three pillars. The year, month and day pillars are unaffected. You will lose the hour pillar’s information about later life, children and inner character.
Which calendar should I enter — solar or lunar?
Enter your ordinary solar (Gregorian) birth date. The conversion is handled internally against a verified lunar table covering 1920–2039.
Is the Day Master the same as a zodiac sign?
No. Your zodiac animal is the branch of your year pillar. Your Day Master is the stem of your day pillar, and it is far more personal — it changes daily, not annually.