BaZi vs Korean Saju

八字与韩国四柱 · 사주

They are the same method under two names. Saju (사주) is the Korean word for the four pillars (四柱); the arithmetic, the pillars, and the day-stem reference point are shared. The real differences are language, consultation culture, and each country's clocks.

Are BaZi and Saju the same system?

By descent, yes. The method entered Korea in the late Goryeo period, and Korean references trace it to the same source Chinese practitioners cite: the Yuanhai Ziping(渊海子平, Song dynasty) and Xu Ziping himself. The full Korean name, sajupalja (사주팔자), is simply 四柱八字 — “four pillars, eight characters” — read in Korean. The reference point for the person, ilgan (일간, 日干), is the day's stem: the same concept this site calls the Day Master. So “BaZi vs Saju” is not a comparison of two systems; it is one Chinese method and what became of it on the peninsula. The honest comparison is between the traditions around it, not the arithmetic inside it.

What is actually different?

Three things, none of them the math. The language: every term is a hanja compound read in Korean — 일주 (ilju) for the day pillar 日柱, 만세력 (manseryeok, 萬歲曆) for the perpetual almanac used to look pillars up. The culture: in Korea, saju consultation is an ordinary commercial service — a thing you might do casually and socially — where Chinese BaZi practice runs more private. And the later development: as the day-master page's lineage table shows, the three East Asian traditions diverged in vocabulary and emphasis over time — Japan's Shichū Suimei (四柱推命), for instance, renamed the Ten Gods 通変星, a naming with no counterpart in the Chinese originals. Same trunk, different branches.

Does a Seoul birth need time corrections too?

Yes — Korea has the same class of clock problem this site keeps writing about for China, and it is usually left out of English Saju material. South Korea's standard time runs on the 135°E meridian, but Seoul sits at about 126.9784°E, so the longitude part of true solar time alone is (126.9784 − 135) × 4 ≈ -32minutes. Per the IANA time-zone database, Korea also ran a UTC+8:30 standard from 1954 to 1961, and daylight saving in stretches of 1948–1960 and again in the summers of 1987–88 for the Seoul Olympics. Each of these can move a birth across an hour-pillar boundary — the same failure mode as China's 1986–1991 DST that breaks most AI tools. A chart cast from raw clock time, in either country, is a chart that has not yet been checked.

Why does this site say “Day Master” and not “Ilgan”?

Because we describe the Chinese tradition, and we would rather keep the three traditions distinct than blur them for convenience. Much English writing about the day stem leads with Saju vocabulary — which is not wrong about the concept, it is describing a Korean transmission of a Chinese method. But the later vocabularies genuinely diverged, and a reader who mixes them will eventually cite a Japanese term to a Chinese text or vice versa. Our pages read the Chinese primary literature and keep its terms, glossed; the Day Master page lays the three lineages side by side so you can see exactly where they connect.

Cast the same pillars yourself

Whether you come to this from BaZi or from Saju, the pillars are the same pillars. Cast your chart — free, no account; the birthplace search covers Seoul and applies the meridian gap and the historical clock changes above automatically, with every convention published on the method page.

The other pages in this series compare BaZi with systems that really are different: Western astrology, MBTI, and Human Design. For the concept the two traditions share at the centre, read the Day Master.