Saju vs BaZi: is Korean saju the same as Chinese BaZi?

Are saju and BaZi the same thing?

Saju and BaZi are two names for one system. Saju (사주, 四柱) means "four pillars", and Koreans also call the chart palja (팔자, 八字), "eight characters". Mandarin reads those same two characters, 八字, as bāzì. Wikipedia's article on the Four Pillars of Destiny gives BaZi as the Chinese name and saju as the name used in Korea, and says the Korean system follows the same structural principles as the Chinese method.

A saju chart and a BaZi chart are written with the same characters. Each of the four pillars, for the year, month, day and hour of birth, pairs one of ten Heavenly Stems with one of twelve Earthly Branches. Only the pronunciation differs. The example chart on the saju calculator is 乙亥, 己卯, 乙巳, 癸未. A Korean reads those pairs as eulhae, gimyo, eulsa and gyemi. In the Mandarin readings listed by the Hong Kong Observatory they are Yi-Hai, Ji-Mao, Yi-Si and Gui-Wei.

Saju and BaZi are also read from the same starting point. The Encyclopedia of Korean Culture says a saju reading centers on the stem of the day pillar, which Koreans call ilgan (일간, 日干). Wikipedia calls the same character the Day Master (日主, rìzhǔ) or Day Stem (日干, rìgān), and credits the four-pillar, eight-character form to the Song-dynasty scholar Xu Ziping. The page on what saju is follows that history into Korea.

The rules that set each pillar are shared as well.

Will a BaZi calculator give me the same chart?

A BaZi calculator and a saju calculator return the same eight characters whenever they are set up the same way. When two charts of one birth differ, the cause is a setting, and it is nearly always a setting about time.

The year and month pillars are the stable half of a chart. Their boundaries are solar terms, and a solar term happens at one instant for the whole planet. This site compares the birth and the term as absolute instants, so the result does not depend on the country. On February 4, 1995, the first minute that gets the new year pillar 乙亥 is 16:13 on the Seoul clock and 15:13 on the Beijing clock, which is the same moment. Two calculators disagree on these pillars mainly when one of them changes the year on January 1 or at Lunar New Year, or the month on a calendar date.

The day and hour pillars are where charts part. They depend on what time it was at the birthplace, and that question has four settings.

None of these four settings is specifically Korean or specifically Chinese. The Encyclopedia of Korean Culture records more than one practice inside Korea, so there is no single official Korean standard. The sections below show what each choice does to a chart on this site. They do not describe the settings of any other calculator. Check those settings in the calculator you are comparing with.

Why is the Korean clock about 32 minutes ahead of the sun?

Korean standard time is set by a meridian eight degrees east of Seoul. Korea's Standard Time Act fixes standard time by the meridian of 135 degrees east longitude, which gives UTC+9. Seoul lies near 127 degrees east. The IANA Time Zone Database gives Seoul's local mean time as UTC+8:27:52, so a clock on UTC+9 runs 32 minutes and 8 seconds ahead of mean solar time in Seoul.

The gap has changed with the law. The table lists the Seoul clock as the IANA database records it.

Daylight saving time adds an hour to the gap. According to the same database, South Korea observed it in 1948 to 1951, 1955 to 1960 and 1987 to 1988. A birth time recorded in Seoul in the summer of 1988 comes from a clock about an hour and a half ahead of the sun.

Some Korean practitioners allow for this gap. The Encyclopedia of Korean Culture notes that the turn of the day is sometimes adjusted to the person's location, and that for Seoul 0:32:47 on the clock is then taken as the start of the new day. Moving every two-hour boundary half an hour later on the clock, so that 子 hour begins at about 23:30, is the same adjustment in round numbers.

A fixed half hour and a computed solar-time correction are not the same setting. The two give different results in the UTC+8:30 years, in a daylight-saving summer and away from Seoul's longitude. They also differ through the seasons, because of the equation of time, the difference between sundial time and mean time. Across 1995, this site's correction for Seoul runs from 47 minutes in mid-February to 16 minutes around the start of November. About and method gives the formula.

Is the solar-time correction only a Korean issue?

No. Any place whose clock follows a distant meridian has a gap of the same kind. The IANA Time Zone Database represents China's legal time as a single zone at UTC+8, with the comment "Beijing time, used throughout China", and records daylight saving time under the People's Republic from 1986 to 1991. One clock over a wide country means the gap depends on the city.

The table takes one clock time, 13:20 on March 15, 1995, in five cities. Each row comes from this site's engine, run once with the city chosen as the Birthplace and once with only the city's time zone.

The day pillar is 乙巳 in every row. By the clock, all five births fall in 未 hour. By solar time, four of them fall in 午 hour, and the correction moves the Chengdu birth further than the Seoul birth. The choice between the clock and the sun applies to a BaZi chart as much as to a saju chart.

How much do these settings change a Seoul chart?

The effect is all or nothing: a chart either stays the same or changes by a whole pillar. The table shows four Seoul births, each run twice on this site's engine. The first run chooses "Seoul, South Korea" as the Birthplace, which uses true solar time. The second chooses "Not listed (choose a time zone)" with Asia/Seoul, which uses standard clock time with any daylight saving hour taken off.

The first row of the Seoul table is the example chart on the home page. Its solar time is 42 minutes behind the clock, and both readings stay inside 未 hour, so the two charts are identical. The second row is the same day, 70 minutes earlier. The clock reading is still in 未 hour, but solar time has dropped back into 午 hour, and the hour pillar changes from 癸未 to 壬午. With a 42-minute correction, this happens to any birth in the first 42 minutes of a two-hour period on the clock.

The 1958 row shows why the year matters. Seoul was then on UTC+8:30, so the correction is only 12 minutes and the birth stays in 未 hour. A flat half hour taken off the same time would give 12:50, which is in 午 hour.

The 1988 row shows daylight saving time. The clock was on UTC+10, so solar time is 98 minutes behind it. Both readings in the table take the summer hour off and arrive at 甲午. A reading that keeps 13:20 as it stands lands in 未 hour: run on this site's engine under a zone with no daylight saving time that year, the same clock time gives 乙未.

You can repeat any of these runs on the home page. The first line under "How this chart was calculated" states which basis a chart used and, for true solar time, the size of the correction in minutes.

When does the day pillar change: 23:00, midnight or 0:32?

The Encyclopedia of Korean Culture describes more than one way to start a saju day. It says some practitioners split 子 hour into yajasi (야자시, 夜子時, 23:00 to 0:00) and jeongjasi (정자시, 正子時, also written 朝子時, 0:00 to 1:00) and set the day pillar differently for the two halves. Under that split, a birth in the hour before midnight keeps the day pillar of the old day. Without the split, the whole of 子 hour belongs to one day, and the new day's pillar begins at 23:00. The encyclopedia also records the Seoul adjustment described above, which moves the dividing point to 0:32:47 on the clock.

This site changes the day pillar at 23:00 true solar time and does not split 子 hour. The table reads one birth three ways: 23:10 on the Seoul clock on March 15, 1995.

In the first row, solar time is 22:28. That is still 亥 hour, so the day has not turned. In the second row the clock has already entered 子 hour, and the chart takes the pillar of March 16. The third row follows from the definition of yajasi: the birth is in 子 hour but keeps the day pillar of March 15.

The stem of the day pillar is the Day Master, the character the whole chart is read from. For this birth in the last hour of the day, the time settings decide whether the chart is read as 乙 or as 丙. That is the largest effect any setting on this page can have.

How do Korean saju terms map to BaZi terms?

The vocabulary of saju is the vocabulary of BaZi in Korean pronunciation. This site prints the Korean reading together with the usual English BaZi name, as in "Day Master (ilgan)" or "Pyeongwan (Seven Killings)". The Mandarin readings in the two tables follow Wikipedia's article on the Four Pillars.

The ten gods keep the same characters in both traditions. Only the seventh is listed under two names.

Four more Korean words are worth knowing. The Encyclopedia of Korean Culture calls the ten relations yukchin (육친, 六親, "six relations"). It calls the twelve life stages sibi unseong (십이운성, 十二運星). The almanac that lists the pillars is the manseryeok (만세력, 萬歲曆). Comparing two charts is gunghap (궁합, 宮合).

The characters are the safest thing to carry between the two vocabularies. If you take a chart to a BaZi reader or to an AI assistant, give the eight characters as computed and say which time settings produced them. The ChatGPT saju prompt on this site is built that way: it carries the computed pillars and the lines that say how the birth time was handled.

What does Korean saju practice emphasize?

As far as the sources used for this page show, Korean saju practice works with the same tools as BaZi, and the differences are matters of emphasis and wording. The Encyclopedia of Korean Culture describes a saju reading as centered on the day stem. It lists what the reader examines: combinations and clashes between stems and branches, the six relations, the balance of yin and yang, how the five elements produce and control one another, the twelve life stages, the twelve sinsal (십이신살, 十二神煞), lucky and unlucky stars, and relations such as punishment and wonjin. It says the reading gives most weight to the yongsin (용신, 用神), the element that brings the chart back into balance.

Wikipedia's description of a BaZi reading covers the same ground: the Day Master and its strength, the balance of the five elements, the ten gods and the luck cycles. It adds that Korean interpretive traditions developed independently, without listing them. This page does not rank the two.

Special stars (sinsal) appear on this site under their Korean names. The result lists 16 noble stars (gwiin, 귀인, 貴人) and three others: Dohwa (桃花, Peach Blossom), Yeokma (驛馬, Traveling Horse) and Hwagae (華蓋, Canopy Star). Stars are looked up from the eight characters by fixed tables, so a longer or shorter star list elsewhere does not mean a different chart. Compare the eight characters first.

Gunghap has a place of its own in Korea. The Encyclopedia of Korean Culture defines it as judging, from the saju of a bride and groom, whether the two suit each other as spouses, and describes it as a step in the traditional marriage procedure. The entry says the custom is fading, yet some people still decide for or against a marriage on the result. On this site gunghap is a separate tool, the saju compatibility calculator.

Is saju a kind of astrology?

Saju is often introduced in English as Korean astrology, and Wikipedia describes the Four Pillars as "a Chinese astrological and calendrical system". Of those two words, calendrical is the one that describes the calculation. The eight characters are date labels. The Hong Kong Observatory explains that pairs of stems and branches have been used to record years, months, days and hours. A saju chart is those four labels for the moment of one birth.

The sky enters a saju chart in two places only. The solar terms, which follow the Sun, start the year pillar and each month pillar; Wikipedia calls the system a solar-based calculation for that reason. On this site, the Sun's position at the birthplace also sets the time of day used for the day and hour pillars. The phase of the Moon, the planets and the constellations are not inputs. That is why the same birth details always give the same eight characters under the same settings.

The twelve animals belong to the calendar too. An animal is the Earthly Branch of a pillar, and the familiar zodiac year is the branch of the year pillar, as the page on Korean zodiac color animals explains. What a reader then says about the eight characters is traditional interpretation. Neither saju nor BaZi is a tested science, and this site describes what the tradition reads into a chart without predicting events.