About
Saju β the Four Pillars of Destiny β is an East Asian system that reads the exact moment of a birth as four pairs of characters. This site computes those pillars for people who do not read Korean or Chinese, and explains what it found.
What this is
Western astrology and Saju are different systems asking different questions. Western astrology places the planets; Saju divides the moment of birth into year, month, day and hour, and reads the relationships between the ten heavenly stems and twelve earthly branches that result.
There is no Saju in a Western birth chart β not because one is better, but because the two traditions were built from different pieces. If you already read your own natal chart, this is a second vocabulary for the same moment.
Why it was built this way
Saju is unusually sensitive to time. The year pillar turns at Start of Spring, not on New Year's Day. The month pillar turns at a solar term that can fall seconds before midnight. The hour pillar depends on where the sun actually was in your sky, which is not what your clock said.
So the arithmetic was built first and the interpretation second. The engine converts a birth moment through four separate corrections, compares absolute instants in UTC where that is what the tradition requires, and uses apparent solar time where that is what it requires. How it is calculated sets out each step, and the places where the answer is genuinely uncertain.
Languages
Readings are available in English, Korean, French and Spanish. The calculation is identical in every language β only the presentation changes. Traditional terms are given with a plain-language gloss rather than left untranslated.
What it deliberately does not do
- It does not predict events. No dates for outcomes, no naming of what will happen. It reports a structure and the tendencies that structure suggests.
- It gives no medical, financial or legal advice. Nothing here is a basis for a decision about health, money or law.
- It does not claim calibrated accuracy. The interpretation rules are our own heuristics. They have not been validated against expert consensus or real outcomes, and every reading says so.
- It does not hide its limits. Time zones before 1970 are not guaranteed by the underlying data, and the chart says so rather than quietly presenting a guess as a fact.
Birth data
If you use the calculator without an account, your birth details are not stored in any profile. Signing in is optional and exists so that a chart can be saved and reopened without typing it again.
The Privacy Policy sets out exactly what is kept, for how long, and who else sees it β including the one third party that receives interpretation text.
Sources and licences
- Solar term instants β computed with astronomy-engine (MIT), cross-checked against the Korean Astronomy and Space Science Institute.
- City coordinates and time zones β GeoNames (CC BY 4.0).
- Time zone history β the IANA time zone database, pinned to a fixed version.
The full list is on Data sources and licences.
Who runs this
For anything else β corrections, a chart that looks wrong, a data or privacy request β see Contact. If you think a chart is miscalculated, please include the birth date, the place you selected and what you expected; that is usually enough to reproduce it.