General concepts

Saju (Korean Four Pillars)

Also known as: sajusaju palja사주사주팔자korean four pillarskorean four pillars of destinykorean astrologykorean birth chartsaju calculatorsaju readingfour pillars koreailgan일간sipseong십성sipsin십신cheonganjijijijangganohaengdaeunyongsinipchun입춘bazi

Saju (사주), "four pillars", is the Korean name and practice of the Four Pillars method, the same calculation as Chinese BaZi: the year, month, day and hour of birth each form a pillar of one stem and one branch, eight characters in all (Saju Palja, 사주팔자).

The word Saju (사주) means "four pillars". It usually appears in its full form, Saju Palja (사주팔자), "four pillars, eight characters", and it is the Korean name, and the Korean practice, of the Four Pillars method that China calls BaZi. The calculation is the same one. The year pillar changes at Ipchun (입춘), the Korean reading of Li Chun, the Start of Spring, around 4 February, and not at the lunar New Year. The months begin at the twelve Jie solar terms, the days run through an unbroken cycle of sixty, and the hour pillar covers a double hour of two clock hours. The four pillars are called yeonju (연주) for the year, wolju (월주) for the month, ilju (일주) for the day and siju (시주) for the hour.

What differs between countries is the vocabulary and the habits of reading. The ten Heavenly Stems are cheongan (천간): gap 갑, eul 을, byeong 병, jeong 정, mu 무, gi 기, gyeong 경, sin 신, im 임 and gye 계. The twelve Earthly Branches are jiji (지지): ja 자, chuk 축, in 인, myo 묘, jin 진, sa 사, o 오, mi 미, sin 신, yu 유, sul 술 and hae 해. The stem of the day pillar, the Day Master, is the ilgan (일간) and is the reference point of the whole chart. How every other stem relates to it gives the Ten Gods, sipseong (십성), sometimes called sipsin (십신). The stems hidden inside the branches are the jijanggan (지장간), and the five phases are the ohaeng (오행). Because a Korean source writes all of these in Hangul, a chart from a Korean app can look unfamiliar next to a Chinese one, although each name stands for the same sign and the same relation.

Saju is widely consulted in Korea, and traditionally people often turn to it at moments such as before a marriage or at the start of a new year. Like BaZi, it is a symbolic system and a cultural tradition, not a science. What this entry describes is how the tradition reads a chart, never what will happen to anyone, and there is no evidence that eight characters fix a person's character or events.

One practical difference matters for the calculation: the clock. Korean Standard Time is reckoned from the meridian 135°E, but Seoul lies near 127°E, so the Sun culminates about 32 minutes after clock noon. For this reason many Korean apps move the birth time back by about 30 minutes before they draw the hour pillar, and the shift can change the hour pillar and, near midnight, even the day. AstroSensus offers this as the option "Solar time at the birthplace", which uses the longitude of the birthplace and the equation of time, a correction that adds up to about 16 minutes more or less depending on the season. The default is the official clock time. South Korea's clock also has an unusual history: it used UTC+8:30 from 1954 to 1961 and summer time in 1948–1951, 1955–1960 and again in 1987 and 1988. AstroSensus applies all of this automatically from the time-zone database, so you enter the clock time as it was on the day.

Korean practice often goes on to name the useful element, yongsin (용신), and to read the ten-year luck cycles, daeun (대운). Schools disagree about the rules for both, and AstroSensus does not calculate them.

The free Saju calculator in AstroSensus uses the same engine as the BaZi calculator and shows the Korean names beside the Chinese ones: the four pillars with their stems and branches, the Day Master, the hidden stems, the Ten Gods and the count of the five phases. It needs no account, uses no AI, and keeps the birth data only in the session.