How Sajoo calculates your chart

Fortune sites rarely show their work. We'd rather you see it: every chart on this site comes out of one deterministic engine implementing the traditional rules, and this page describes exactly what those rules are. Enter the same birth date twice and you'll get the same chart twice — there's no improvisation in the math.

The calendar engine

Charts are computed with 만세력 (perpetual calendar) rules — the same tables a traditional Korean reader keeps on the shelf. The backbone is the sexagenary cycle: ten heavenly stems and twelve earthly branches pairing into sixty combinations that years, months, days, and hours all rotate through.

The day pillar — the one that carries your Day Master — is a continuous 60-day count, unbroken across months, years, and calendar reforms. It isn't derived from the date's digits; it's a running count, which is why it can only be computed, never guessed.

The year boundary: astronomical ipchun

The year pillar turns at ipchun (입춘 · 立春), the first solar term, in the February 3–5 window. Rather than using an approximate lookup, the engine computes the sun's apparent longitude for your birth year and cuts the boundary at the true ipchun moment. Born February 4? The math of your actual year decides your animal — not a lookup table that assumes the most common date.

What we don't fill in

If you don't provide a birth time, the hour pillar stays empty. Six of eight characters — including the Day Master, the element balance, and the zodiac animal — don't depend on it, and inventing the other two would be dishonest. Blank means blank.

The same engine runs behind every answer Sajoo gives: the free chart, the zodiac finder, the paid readings, even the replies we leave on Instagram comments. One code path, one answer, every time.

Interpretation and its sources

Calculation is mechanical; interpretation is a tradition. Our interpretive frames — the Day Master nature images, the ten-gods relations, the special stars, the 궁합 layers — follow the Ziping (자평) school of four-pillars reading that Korean practice inherits, the lineage running through classical texts like 연해자평 and 자평진전. The English wordings are our own; the structures underneath are the tradition's.

And the stance, always: saju here is for fun and self-reflection. We compute your chart honestly and read it in the tradition's language — as a mirror of temperament, never as a prediction, a guarantee, or advice.