Saju, BaZi and 四柱推命: what’s the same and what differs

What all three share

All three traditions write a birth moment as four pillars, each a heavenly stem over an earthly branch, and read the chart from the day stem outward. The Korean encyclopedia entry for 사주 describes exactly this structure: year, month, day and hour, each written with a stem and a branch (사주, E0025957). Japanese dictionaries define 四柱推命 the same way, and say it matured in Song-dynasty China (Kotobank: 四柱推命).

They share the working vocabulary too: the five elements, the ten gods derived from the day stem, hidden stems inside each branch, the twelve stages and ten-year luck pillars. All three draw on the same classical Chinese handbooks, such as the Ming compendium 三命通會 (三命通會, vol. 5) and 淵海子平, which lists the ten gods using a 甲 Day Master as its example (淵海子平).

Side by side: where the three differ

Differences are mostly names and habits. We mark a row “observed practice” when it describes what readers and apps commonly do rather than a rule written in a source, so you can weigh it accordingly.

What’s distinctly Korean about saju

Three habits stand out. First, 궁합 (gunghap) as a marriage custom: the Encyclopedia of Korean Culture describes the bride’s family receiving the groom’s birth details and having both charts compared, by the zodiac branches on the surface and by the five elements underneath (궁합, E0006817).

Second, the love of 신살 (sinsal), short named signs such as 도화살 (a “peach blossom” sign linked with charm) and 역마살 (a “post horse” sign linked with travel). They come from the same Chinese stock as BaZi’s 神煞, and in Korean pop culture they work as everyday shorthand. We treat them as folklore labels, not verdicts.

Third, the clock. Korea set its standard meridian at 127°30′E (UTC+8:30) in 1954 and moved it to 135°E (UTC+9) in 1961, where it has stayed (시법, E0032366). At four minutes per degree, the middle of the peninsula runs about 30 minutes behind the clock by the sun, and Seoul about 32. Some Korean 만세력 (manseryeok) apps and readers therefore run the two-hour periods on half-hour boundaries, with the Rat hour from 11:30 p.m. to 1:30 a.m. (정해 만세력, lecture 08); others keep clock hours.

Where BaZi and 四柱推命 put their weight

In Chinese practice the tradition is often called 子平 after Xu Ziping. The Ming handbook 三命通會 opens its discussion of the chart’s key stars by saying Xu Ziping organized chart patterns around four of them: resource, eating god, officer and wealth (三命通會, vol. 5). Many Chinese readings center on chart strength and a “useful god” (用神) that balances it.

Japanese 四柱推命 keeps classical names such as 印綬 for Direct Resource and calls the ten gods as a set 通変星 (Kotobank: 通変星). Japanese calculators commonly add a second row of ten gods for the hidden stems and a “central star” (中心星) from the month branch, and the 空亡 void and 天中殺, from the related 算命学, are popular topics (observed practice). A frequent source of disagreement between Japanese sites is which hidden stem to use for a given birth date, not the pillars themselves.

What isn’t different, whatever you read

Some comparison pages claim Korean saju is more personal, more insightful or more obsessed with one part of the chart. We haven’t found a source for sweeping claims like that. What the handbooks and dictionaries show is one craft with local vocabulary and local favorites.

Nor is your chart different by country. A birth in New York at 7:40 AM on Nov 2, 1994, is 甲戌 甲戌 壬辰 甲辰 whether a Korean, Chinese or Japanese calculator computes it, as long as they use the same time zone, day boundary and solar-term instant. When two sites disagree, check those settings first (how we calculate).

A short history in each country

China: Japanese reference works say the method began in ancient China and reached its finished form in the Song dynasty, and one of them says the Tang-dynasty figure Li Xuzhong (李虛中) is revered as its founder (Kotobank: 四柱推命). Others give that title to Xu Ziping (徐子平), because the oldest surviving book on the method is his, from the Song (Japanese Wikipedia: 四柱推命).

Korea: by the Joseon dynasty the state observatory examined candidates on a book named after Xu Ziping, and the court read saju at least once for royal marriage candidates, in 1515 (what is saju).

Japan: the earliest Japanese book on the method that is usually cited is 推命書 (Suimeisho) by Sakurada Komon, whose preface is dated 1818 (National Diet Library record). Sakurada was a Confucian scholar in the service of the Sendai domain (Kotobank: 桜田虎門). Japanese Wikipedia describes the book as a Japanese rendering of the Chinese handbook 淵海子平 (Japanese Wikipedia: 四柱推命), and the library holds later printings from 1831, 1884 and 1901. Today, the Heibonsha World Encyclopedia notes, Japan still has many devotees, who treat the books of Abe Taisen (阿部泰山) as required reading.

Which one should you use?

Use whichever language you read comfortably. The chart is the same; what changes is the vocabulary and the extra signs a reader likes. A Chinese BaZi calculator works for a Korean saju reading as long as it counts the year from Ipchun and you enter the same time zone; if you were born in Korea and the hour matters, check whether it applies the half-hour shift. Compare the calculation settings first, then the interpretation.

Where Horan’s Saju Room sits

We use Korean names and a Korean frame, with the calculation made explicit: local clock time in your birthplace’s time zone (no half-hour or solar-time shift on the chart form), midnight as the day boundary, the three-stem 人元 hidden-stem table with the main stem first, and no scoring of strength or useful god (our settings). The characters, Horan and Kachi, are fiction; the paid readings are written with AI and are for entertainment and self-reflection.

About this page

Written with AI (Claude) from the sources listed and our calculation engine. Horan and Kachi are fictional characters, and nothing here predicts events. The rules behind every chart: how we calculate.