Saju is a conversion before it is an interpretation. Before anyone says anything about your character, a birth moment has to become eight characters. That step is arithmetic, and it is the part most people never see.
Step one: fix the moment. Date, time, and place. The place matters because it determines the timezone, and timezones have history — Korea has changed its standard offset more than once, and daylight saving has come and gone in many countries. A calculator that assumes today's offset applied in 1988 will produce the wrong hour pillar, and sometimes the wrong day pillar for births near midnight.
Step two: find the four pillars. Each pillar is a heavenly stem (천간) over an earthly branch (지지). There are ten stems and twelve branches; run them in parallel and they align every sixty steps. That sixty-step cycle numbers years, days, and hours.
- The year pillar comes from the Saju year, which turns at 입춘 (start of spring, around 4 February) — not 1 January.
- The month pillar comes from solar terms (절기), astronomical points along the sun's path. Months do not begin on the first of the calendar month.
- The day pillar comes from continuous day counting through the sixty-cycle.
- The hour pillar comes from two-hour blocks, with the stem derived from the day stem.
Step three: read the relationships. Eight characters, each carrying an element and a polarity. The Day Master — the stem of the day pillar — becomes the reference point, and everything else is described in relation to it through the Five Elements and the Ten Gods.
Everything up to step three is deterministic. The same birth minute in the same place always produces the same eight characters, and the result can be checked against a traditional 만세력. Interpretation is where judgement enters, and it should be labelled as such rather than dressed up as calculation.
For entertainment and self-reflection only. Not advice.