What is SJPJ? The Korean saju trend, explained

If you've seen people online calling themselves a "Red Sun" or a "Blue Tree," or saying Korea has a new MBTI, this is what they're talking about.

SJPJ is an abbreviation of saju palja (사주팔자), the Korean name for a traditional birth-chart system. The words roughly mean "four pillars, eight characters." It's the same system known in Chinese as BaZi, and it has been used across East Asia for a very long time. In Korea it never really went away — people still check saju before weddings, big moves and job changes — and younger Koreans have started using it the way they use MBTI: as a shorthand for who someone is.

Four pillars, eight characters

The chart is built entirely from when you were born. Four moments, one "pillar" each:

Each pillar has two characters: one of ten "heavenly stems" on top and one of twelve "earthly branches" underneath. Four pillars times two characters is eight. That's the palja.

A few details catch people off guard:

• The year doesn't start on January 1. It starts at ipchun, the traditional start of spring, around February 4. If you were born in January, your saju year is the previous one.
• The months don't match calendar months either. They follow the 24 solar terms, so each saju month begins somewhere around the 4th to 8th of a calendar month.
• The day just keeps counting. Day pillars run in a 60-day cycle that has been going continuously for thousands of years, which is why you need a lookup table (a manseryeok) or a calculator. There's no shortcut from the date.
• The hour comes in two-hour blocks. If you don't know your birth time, you get six of your eight characters, which is still most of the reading.

The part people post about: the day master

Of the eight characters, the top one on the day pillar matters most. It's called your day master, and the whole chart is read around it.

There are only ten. Each is one of the five elements — wood, fire, earth, metal, water — in a yang (bigger, outward) or yin (finer, inward) form, and each has a traditional image: the Tall Tree, the Vine, the Sun, the Candle, the Mountain, the Garden, the Sword, the Jewel, the Ocean, the Rain. The "Red Sun" and "Blue Tree" labels online come from the traditional color of each element — green-blue for wood, red for fire, yellow for earth, white for metal, black for water.

All ten day masters are explained here, with what each one is describing.

Why it's getting called the new MBTI

Mostly because it scratches the same itch. A small set of types, each with a memorable name, that you can compare with friends, check for compatibility, and argue about.

But the two work very differently, and it's worth knowing how:

The fixed part is what people either love or can't stand. MBTI says "this is how you tend to act." Saju says "this is what you were born with," and then the rest of the chart — the other seven characters — describes what's pulling on it.

What it can and can't tell you

Saju is a traditional system, not a science. There's no evidence your birth date sets your personality, and a good saju reader will tell you the chart is a starting point for a conversation, not a verdict.

What it's genuinely good at is giving you a vocabulary. "I'm a Mountain dating an Ocean" is a fast, memorable way of saying "I'm steady and they're restless, and we both know it." That's the same reason any personality system spreads — the words are useful even if the mechanism is disputed.

If you want to try it without looking anything up, the day master quiz finds which of the ten you act like from twelve questions. Then look up your real one with a calculator and compare. When the two don't match, that's usually where the interesting conversation starts.