What this site is
Four Pillars of Destiny is a free, browser-based calculator for the Korean Four Pillars (사주, Saju) tradition — a descriptive East Asian system that maps the year, month, day, and hour of a birth into a chart of cosmic symbols. The calculator and the interpretive text on this site are written originally in English, for English-speaking readers curious about the tradition.
The site is built as a single static HTML file with the calculation engine implemented in plain JavaScript. There is no AI, no third-party API, and no data collection. The only network calls are the Google AdSense ad tags required for site monetization.
Our mission
We want to make the Four Pillars tradition accessible to readers who don't read Korean, Chinese, or Japanese, while being honest about what the tradition is and what it is not.
- Descriptive, not predictive. The Four Pillars tradition offers symbolic language for reflection — it does not forecast specific events.
- Educational, not fortune-telling. We present the system as a piece of cultural heritage, not as a paid service that promises outcomes.
- Private by default. Birth data never leaves your browser. No account. No cookies. No analytics on personal input.
Methodology
The calculation engine uses three components:
1. The 60 Sexagenary Cycle (60 갑자 / 六十甲子)
The traditional East Asian cycle that pairs the 10 Heavenly Stems (天干) with the 12 Earthly Branches (地支) into 60 unique combinations. The cycle repeats every 60 years, months, days, or hours, and is the mathematical backbone of the Four Pillars system.
2. Solar Term (절기) Boundaries
Months in the Four Pillars tradition begin at the 12 zhōngqì (中氣) solar terms, not on the first of the Gregorian month. Our implementation uses the standard approximate dates for these terms (e.g. 입춘 / Start of Spring on February 4). This is the conventional trade-off: ±1 day of accuracy near the transition in exchange for a small and auditable codebase. For a more precise implementation, an embedded per-year solar-term table would be required.
3. Julian Day Number (JDN) for the Day Pillar
The Day pillar is the most precise component. We compute the Julian Day Number of the input date and apply the well-known formula stem = (JDN − 11) mod 10, branch = (JDN + 1) mod 12. This has been verified against the reference Jan 1, 2000 = 戊午 day.
Lunar input
For users entering a Korean or Chinese lunar birth date, the site converts to the solar (Gregorian) date using a 1900–2099 lookup table of lunar month lengths. The reference point is the well-known Jan 31, 1900 = Lunar 1900-01-01.
Source references
The interpretive text draws on the broader English-language Saju / BaZi literature and is curated for accuracy and neutrality. We do not claim that any single reading is the "official" interpretation — Saju interpretation varies across schools and centuries.
The Four Pillars tradition is one of the world's oldest symbolic systems. Like any symbolic system, it is a lens, not a lens prescription.
Editorial principles
- We do not promise specific life outcomes.
- We do not provide medical, psychological, financial, or legal guidance.
- We do not collect personal data.
- We disclose any advertising clearly.
- We use cookies only when strictly necessary and disclose them on the Privacy Policy page.
About the calculations
The complete source code is publicly available on the project's GitHub repository. You can verify the algorithm yourself, audit it for correctness, and even run a Node.js test suite against known reference dates.
Contact
Questions, corrections, or feedback? Visit the Contact page.