What this is, and how it works

We'd rather tell you the real story than a flattering one.

What saju is

Saju (사주, “four pillars”) is Korea's practice of reading a person from the year, month, day and hour of their birth. Each of the four moments is written as a pair of characters, a “heavenly stem” and an “earthly branch”, drawn from a sixty-term cycle; the eight characters together are the chart. The method itself is older than Korea's use of it: it grew out of classical Chinese Four Pillars (四柱, often called BaZi in English), systematised around the 10th century. Korea did not invent the arithmetic, and we won't claim it did.

What Korea did was make it its own. A few things are distinctly Korean:

• Tojeong Bigyeol (토정비결). A yearly reading unique to Korea that uses three of the four pillars to lay out a year month by month. Many Koreans still check it at Lunar New Year.
• The tone. Chinese BaZi is often analytic, almost clinical. Korean saju leans toward counsel: a reader spends half the session listening. That is the voice we tried to give Master Haneul.
• Marriage. In the Joseon period, families exchanged a written birth chart (사주단자) before a wedding could proceed. Compatibility readings were not entertainment; they were part of the institution.
• Names. Korean naming (작명) treats a name as a way to balance a chart's elements, which is one reason adults sometimes change theirs.

The maths is shared across East Asia. The framing you'll find here is Korean. If you want the mainland Chinese framing, there are good BaZi tools for that; this isn't one of them, on purpose.

How we calculate

The pillars are computed astronomically, not looked up in a calendar table. The month pillar turns on the solar terms, which we compute from the Sun's ecliptic longitude to the minute. Your birth time is corrected to true solar time at your birthplace, using the city's longitude, its historical time-zone rules and daylight saving as they stood on the day you were born. The engine is checked against a set of reference charts before any change ships, and the reading tells you when your birth falls close to a boundary, where a few minutes either way would change a pillar. If you don't know your birth time, we compute three pillars and say so rather than guess the fourth.

Who Master Haneul is

Master Haneul is a persona, not a person. There is no named master, teacher or lineage behind this site, and we don't claim one. The calculation is done by our software; the words of your insight and the answers to your questions are written by an AI language model (from Anthropic) that we instruct to speak in the voice of a patient Korean reader. The model sees your first name and your computed chart, never your exact birth time or birthplace coordinates. Its text can be wrong or generic, and it is not reviewed by a human before you see it. We ask you after your insight whether it sounded like you, and we read those answers to make it better.

What this is not

For entertainment and self-reflection purposes only. Not a substitute for medical, legal, or financial advice. 18+ Readings are for reflection and conversation. Master Haneul declines questions about death, illness, pregnancy, legal outcomes, specific investments and gambling. If you are in crisis, please contact a local helpline; Master Haneul will point you to one rather than answer.

Who runs this

K-Mystic is run by Jusang Company (주상컴퍼니), a sole proprietorship registered in the Republic of Korea. It is a small, independent project, built so that people outside Korea can see their chart computed properly and explained in plain English. There are no accounts and nothing to buy in this version. How we handle your birth details is in the Privacy Policy; the rules of the road are in the Terms of Service. Questions: hello@k-mystic.app.