Saju (四柱) literally means "four pillars." The same system is called BaZi (八字), "eight characters," in Chinese. Both names describe the same chart — they just count it differently: four pillars, two characters each, eight characters in all.
OneThe day master — the character that stands for you
Look at the highlighted column in the chart above. The top character of the day pillar is called the day master. In a Saju reading it is taken to represent you, and the other seven characters are read as your surroundings — what supports you, what you produce, what presses on you.
There are only ten heavenly stems, so there are only ten day masters: each of the five elements in a Yang (outward, direct) and a Yin (inward, flexible) form. Tradition gives each one a picture:
| Stem | Day master | Traditional image |
|---|---|---|
| 甲 | Yang Wood | a tall tree |
| 乙 | Yin Wood | a vine, a flower |
| 丙 | Yang Fire | the sun |
| 丁 | Yin Fire | a candle, a hearth |
| 戊 | Yang Earth | a mountain |
| 己 | Yin Earth | field soil |
| 庚 | Yang Metal | raw ore, an axe |
| 辛 | Yin Metal | a jewel, a fine blade |
| 壬 | Yang Water | a river, the sea |
| 癸 | Yin Water | rain, mist |
So "I'm a Yang Water day master" is a Saju sentence in the way "I'm a Scorpio" is a Western one — except that it comes from your birth day, not your birth month, and two people born a day apart get different ones.
Which one are you?
You can't tell from your birth year — the day stem moves through all ten, one per day. Saju Today works it out from your birth date in a few seconds, free, no sign-in needed.
Find my day master →TwoThe four pillars — where the other seven come from
Your birth year, month, day and hour each become one pillar. Every pillar has a top character, the heavenly stem, and a bottom character, the earthly branch. The twelve branches are the ones you may already know as the zodiac animals — Rat, Ox, Tiger and so on. The sample chart above shows all eight.
Charts are traditionally written right to left, which is why the year sits on the right. Every character belongs to one of five elements, and that is what the colours show.
One thing surprises most newcomers: the "animal year" people know from the zodiac is only one of the eight characters — the bottom of the year pillar. Saju reads all eight, and it does not treat the year as the most important one.
ThreeThe five elements
The elements are not substances. They are five kinds of movement, and the tradition describes each with an image from nature:
木 Wood — growth that pushes upward and outward. Starting, planning, stretching.
火 Fire — warmth and visibility. Expression, enthusiasm, being seen.
土 Earth — the ground that holds things. Steadiness, trust, the middle of things.
金 Metal — shape and edge. Structure, decisions, cutting what is not needed.
水 Water — depth and flow. Listening, adapting, moving around obstacles.
What makes this a system rather than five labels is that the elements act on each other, in two loops:
Feeding
Wood feeds Fire → Fire makes Earth (ash) → Earth bears Metal → Metal gives rise to Water (think of dew gathering on cold metal) → Water feeds Wood
Restraining
Wood breaks Earth → Earth dams Water → Water puts out Fire → Fire melts Metal → Metal cuts Wood
A reading starts here: look at the day master's element, then at what the other seven characters do to it. A Water day master surrounded by Metal is being fed. The same Water surrounded by Earth is being held back. A full reading weighs much more than this — the season of birth, the elements hidden inside each branch, characters that combine or clash — and it judges each influence as helpful or unhelpful for the balance of that particular chart, not in the abstract.
FourWhy the day changes things
The calendar itself runs on the same characters. Today has its own pillar — its own stem and branch, each with an element — and so do this month and this year. A daily Saju reading sets today's pillar against your day master: a day that feeds you, a day you feed, a day that presses on you, a day you press on, or a day that is simply more of what you already are.
A worked example
Take the chart at the top: a Water day master. On a day whose pillar is mostly Earth, the restraining loop applies — Earth dams Water. The tradition reads that as a day of outside pressure: better for finishing what is already under way than for pushing something new. On a Metal day the same person is being fed instead.
That is the starting point of a "daily line." Your chart stays the same for life. The day moves, and the relationship between the two is what gets read.
How Saju Today uses this
Chart shows your four pillars, your day master and how the five elements are balanced across your eight characters. Today reads the current day's pillar against your day master. Week does the same for the days ahead, Match places two charts side by side, and Stars sets your Saju next to your Western astrology chart.
The pillars are calculated in the app from your birth date and time using calendar rules, not a lookup of your zodiac year. The wording of each reading is then written by an AI language model from that chart. Which calendar rules the app uses — and why different apps sometimes give different pillars for the same birthday — has its own page.
Open Saju Today →Saju Today is an entertainment app. Every reading in it is generated by an AI language model (Google Gemini) applying traditional Saju concepts — for reflection and entertainment, not a prediction of the future, and not medical, psychological, legal, or financial advice. This page describes how the four-pillar tradition is structured; it is not a claim that the tradition predicts anything.