Four pillars, eight characters
The traditional East Asian calendar does not write a moment as numbers. It writes it as pairs of characters: one Heavenly Stem (천간, ten of them) on top of one Earthly Branch (지지, twelve of them). A birth has four such pairs, the year, month, day and hour, so a Saju chart is four pillars and eight characters. Koreans call it sajupalja (사주팔자), literally “four pillars, eight characters”.
| Pillar | Comes from | Traditionally read as |
|---|---|---|
| Year | The solar year, which begins at Ipchun (입춘, around February 4), not January 1 | Ancestors, early life, the outside world |
| Month | The solar term (절기) the birth falls in; twelve per year | Parents, career, the season that shapes the chart |
| Day | A 60-day cycle running continuously since antiquity | You (the stem) and your spouse or partner (the branch) |
| Hour | One of twelve two-hour windows in true solar time | Children, later life, the inner self |
The stem of the Day pillar is the Day Master (일간). Everything else in the chart is described by its relationship to it. A Day Master of 甲 Gap is Yang Wood; 癸 Gye is Yin Water. Ten stems, five elements, each in a yang and a yin form.
Five elements and ten gods
Each of the eight characters belongs to one of five elements: Wood, Fire, Earth, Metal, Water. The elements feed and control each other in a cycle, so a chart can be read as a balance. A chart with three Fire characters and no Water reads very differently from the reverse.
Because every character is compared to the Day Master, each one gets a role name. The tradition calls them the ten gods (십신). A character of the same element is a Friend (比肩) or Rob Wealth (劫財); an element the Day Master controls is Wealth (正財, 偏財); an element that controls the Day Master is an Officer (正官) or Seven Killings (七殺); the element that produces the Day Master is Resource (正印, 偏印); the element the Day Master produces is Eating God (食神) or Hurting Officer (傷官). These names are what a reader actually talks about: “your Wealth sits in the Month pillar”, “you have two Officers and no Resource”.
Hidden stems, stars and interactions
- Hidden stems (지장간). Each Earthly Branch contains one to three stems inside it. They matter for strength and for structure, and a good reading always looks at them.
- Symbolic stars (신살). Named patterns such as the Nobleman (天乙貴人), Peach Blossom (桃花) or Travelling Horse (驛馬). Korean readers use them more freely than most Chinese schools do.
- Interactions (합충형파해). Pairs of branches that combine, clash, punish, break or harm each other. A clash between the Day and Month branches is the kind of thing a reader mentions first.
Where Saju comes from
The Four Pillars method was systematised in China around the Song dynasty, usually credited to Xu Ziping, and reached Korea during the Goryeo period. Under the Joseon dynasty it became part of ordinary life, used for naming children, choosing wedding dates and judging compatibility (궁합, gunghap). It never went away: today Koreans consult Saju at the new year, before a marriage or a job change, and increasingly through apps and fortune cafés in Seoul. Korean dramas and variety shows mention it constantly, which is how many people outside Korea first hear the word.
What Saju is used for
- Personality and temperament, read mainly from the Day Master and the element balance.
- Career and money, read from the Wealth and Officer characters and where they sit.
- Relationships and compatibility, read from the Day branch and by comparing two charts.
- Timing: ten-year luck pillars (대운) and yearly luck (세운) describe which periods support or challenge the chart.
What you need to calculate one
Birth date, birth time (or a rough window, or none), and birthplace. The place matters because the Day and Hour pillars are computed in true solar time: noon in the chart is when the sun is highest where you were born, not when the clock says 12:00. A birth in Los Angeles and a birth in Seoul at the same clock time can land in different hour windows. SajuPaste handles this automatically, including historical daylight-saving rules.