How we calculate your chart
Your chart is calculated, not guessed. No AI makes up your pillars: we follow the rules of Korean saju step by step, so the same birth details always give the same chart.
Your birth city's clock, history included
We look up your city in the international time zone database, including any daylight saving time in effect on the day you were born. You don't need to know whether DST applied; we handle it automatically, even for unusual years like Korea in the 1950s.
The sun's time, not the clock's
Saju hours follow the sun. For births outside Korea, we use local mean time from your city's longitude (4 minutes per degree). For births in Korea, we follow the Korean convention of the 127.5°E meridian, about 30 minutes behind the clock.
Example Born at 7:30 a.m. in Chicago in July 1990? Daylight saving time was on, and Chicago sits at 87.6°W, so the sun's time was 6:39 a.m. Your hour pillar is the Rabbit hour (5 to 7 a.m.), not the Dragon hour the clock suggests.
Months start with the solar terms
Saju months don't follow the calendar. Each one begins at a solar term, an exact moment in the sun's yearly path. We use the official times from the Korea Astronomy and Space Science Institute where they are published, and precise astronomical calculation for other years (within about a minute of the official times). The saju year turns at Ipchun (around February 4), not on January 1 or Lunar New Year.
When the day changes
Your day pillar changes at 11 p.m. sun time, the start of the Rat hour (ja-si), as most Korean saju apps do. Some schools change it at midnight instead. We tell you which rule we use rather than hiding it.
Don't know your birth time?
We read your chart from three pillars (year, month, and day) and skip anything that needs the hour pillar. Your result says so, so you always know what it's based on.
From eight characters to your reading
We weigh the five elements across your eight characters, check whether your Day Master (the character that is 'you') is strong or weak, and find the energy you need most. Every step leaves a written reason, and your reading is built from those results, not invented on the spot.
Where saju schools differ
A few points vary between schools, such as when the day changes or how to weigh the hidden characters inside each branch. We use common Korean defaults, apply them the same way for everyone, and plan to review them with a saju expert.
Your birth details
Until you sign up, your birth details stay on your device. We never put your birth date, birthplace, or name into analytics or AI requests.
Questions
Is saju the same as BaZi?
They share the same roots: four pillars and eight characters (BaZi literally means 'eight characters'). Korean saju has its own conventions, like the 127.5° time correction and the way charts are read. We follow the Korean way.
Do you use AI to make my chart?
No. Your pillars and the judgments come from fixed rules, not from an AI guess. That's why the result never changes when you check again.
Another app gave me a different chart. Why?
Usually it's the birth time: many apps use clock time without the sun-time correction or daylight saving time, or change the day at midnight. If you were born near the edge of an hour, those choices can move your hour or day pillar.