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Do Twins Have the Same Saju?
— a 7-minute gap that split the hour pillar, and why boy-girl twins get different Daeun

2026-10-30 · Mutal Unnie editorial team

Do twins have exactly the same Saju?

If they were born within the same sijin (時辰, two-hour period), all four pillars and eight characters are identical; if they crossed an hour boundary, only the two characters of the hour pillar differ. Saju writes the year, month, day and hour of birth as two stem-branch characters each, so twins born on the same day always share the year, month and day pillars. The only pillar that can split is the hour pillar, which changes every two hours.

Let's work through a real calculation with the Mutal Unnie engine: twins born on March 2, 1998, at 10:58 a.m. and 11:05 a.m., seven minutes apart. It's a practice input, not real people.

Both twins have Mu Earth (戊土) as their Day Master, so the character that stands for “me” is the same. The hour pillar is traditionally read as the seat of children, later life and one's inner world: the first-born twin has Direct Resource (Jeong Fire) and Indirect Resource (Sa Fire) there, while the second-born has Companion (Mu Earth) and Direct Resource (O Fire). Think of it as the same root with branches of a slightly different grain. The basic nature of this day pillar is in Musin day pillar (戊申).

Where is the boundary that splits the hour pillar by a few minutes?

The Mutal Unnie app and engine set the boundaries on the odd hours of the clock by default. The O (午, Horse) hour starts at exactly 11:00 a.m., so 10:58 falls in the Sa hour and 11:05 in the O hour. Because the twelve Earthly Branches divide the 24-hour day into two-hour blocks, a few minutes near a boundary can tip a birth into the next block.

Where to draw that line, though, depends on the calculation method. Switch on the true solar time correction in the web manseryeok calculator (for Seoul, about 32 minutes earlier plus the equation of time) and these twins become 10:13 a.m. and 10:20 a.m., both with a Jeongsa (丁巳) hour pillar. Different hour pillars by default, the same hour pillar with the correction.

If the twins were born when Korea's standard time differed from today's, as in 1954 to 1961, or during a daylight saving period, another correction stacks on top. The background is in Korea's Standard Time Changed Three Times, and the day-pillar question for births in the 11 p.m. hour is in Born at 11 p.m.? The Late and Early Ja Hour. Twins born outside Korea face the same logic with their own local clock and any daylight saving time in force there, so always note which time you entered.

Why do boy-girl twins get different Daeun?

In traditional calculation, the direction of Daeun (大運, the 10-year luck cycle) is set by combining the yin or yang of the birth-year stem with the person's gender. In the example, the year stem Mu (戊) is yang, so a male chart runs forward and a female chart runs backward. Even with an identical birth chart, the 10-year rhythm flows in opposite directions.

The starting age comes from the gap between birth and the next solar-term entry (Gyeongchip) for a forward cycle, or between the previous entry (Ipchun) and birth for a backward one. March 2 sits just before Gyeongchip, so the forward cycle starts early, at age 1, while the backward cycle, measured from the more distant Ipchun, starts at 9. The method is explained in Daeun (大運): The Big Rhythm That Changes Every 10 Years, and you can try your own numbers in the free Daeun calculator.

Same-gender twins run in the same direction, and a gap of a few minutes usually gives the same starting age too. In the example above, if both twins were the same gender, their Daeun would come out identical.

How many people have exactly the same Saju as me?

By a simple estimate, a little over 50 people born in Korea in a single year. We'll use Korea as the worked example: 238,300 babies were born there in 2024. The number of Saju combinations possible in one year is roughly 365 days × 12 two-hour periods, or about 4,380. Divide births by combinations and you get an average of about 54 people per combination.

That figure is an average that ignores gender, place of birth and how hour boundaries are drawn. Births aren't spread evenly across dates and hours either, and since Daeun splits by gender, the number of people who share both the eight characters and the Daeun is smaller still. The same arithmetic works for any country: divide its annual births by about 4,380. Either way, it gives a clear sense that a Saju isn't a personal ID number. Twins aren't unusual in sharing a chart; plenty of people share the same eight characters to begin with.

Source: Statistics Korea (Aug 27, 2025), 2024 Birth Statistics (in Korean). The number of combinations and the average are a simple estimate by the Mutal Unnie editorial team.

How does traditional Saju tell twins apart?

There's no agreed standard rule; some schools and readers pass down supplementary methods, and that's all. Myeongni (命理, the study of Saju) is built around one person's birth moment, so it doesn't offer a settled answer for splitting two people born at the same time.

Some readers suggest reading the first-born twin from the chart as it is and shifting the second-born's hour pillar or Daeun by one step. Another view reads the older and younger sibling's places in the family separately through the yukchin (六親, six family relations) framework. These are a reader's perspective, not verified calculation rules, so the Mutal Unnie engine doesn't shift a chart or Daeun just because someone is a twin. If a reader uses such an adjustment, ask what it's based on.

If two people share a Saju, will their lives be the same?

No. Sharing a Saju doesn't make lives the same. Twins with the same eight characters growing up with different personalities and paths is a familiar story to any twin family. Modern Saju readings also treat the chart as a framework for temperament and timing, not a script with the ending already written.

1. Gender and DaeunBoy-girl twins get 10-year cycles running in different directions from different ages, even from the same birth chart.
2. Place in the familyBeing called the older or the younger child often brings different roles and expectations, especially in Korea, where the older twin is still addressed as the elder sibling.
3. Environment and choicesEven in the same home, twins meet different friends and teachers and pick different things. None of that is written in a Saju chart.
4. NamesKorean name study (seongmyeonghak 姓名學) sometimes reads a name together with the Saju, so even twins often get names chosen for each child individually.
5. Birthplace and time recordsUnrelated people who share a clock time may have been born in different places. Under longitude-based corrections, the same clock time can yield a different hour pillar.

What should parents of twins watch for when reading their children's Saju?

Most important: confirm each child's birth time to the minute, and don't use Saju to compare the twins or hand out roles. Twins are born only minutes apart, so times recalled from memory are easy to swap.

1. Confirm the times from recordsCheck each child's time on the birth certificate or hospital records. Where to look in Korea is in How to find your birth time; elsewhere, ask the hospital where they were born.
2. Note the calculation methodNext to each result, write whether it uses clock time as entered or a true solar time correction.
3. Don't copy readings acrossEven if the charts match, don't copy one child's reading onto the other, and if they're different genders, read their Daeun separately.
4. Don't compareDon't decide in advance whose Saju is better, or that one child is a certain way because the hour pillar differs. What the children show you as they grow comes first.

The order for reading parents, children and siblings together is in How to Read Family Saju: Parents, Kids, Spouse and You.

How can I check twins' Saju on Mutal Unnie?

Enter each twin's time and gender separately in the free web manseryeok calculator and the Daeun calculator, and you can compare at a glance which pillar and which Daeun split. The manseryeok calculator lets you switch daylight saving, old standard time and true solar time corrections on or off, which makes it easy to put the before and after side by side for twins born near an hour boundary.

The app calculates from the clock time you enter, treated as Korea time (KST), and doesn't correct daylight saving or old standard time automatically; if you were born outside Korea, see how to enter a local birth time in Korean Saju vs. Chinese BaZi vs. Japanese Shichū Suimei. If you're a twin yourself, build a chart from your own birth time, then use the free one-line rhythm for the day and your mood journal. Even with the same Saju, how each day went shows up differently in the log.

Start with today's rhythm

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