Korean Saju, calculated correctly, explained in English
Two apps from one engine. Jeolgi builds the chart. Gapja reads it.
Saju (사주) is the Korean Four Pillars system: a birth year, month, day and hour are each written as two characters, and the eight characters describe a person. 60Gapja makes two Korean Saju apps for English speakers. Jeolgi is a Saju calculator that shows the solar-term and birth-time corrections behind every pillar. Gapja is a Saju reading app that turns the same chart into plain-English insight about personality, relationships and timing.
Jeolgi — Saju & BaZi calculator
Enter a birth date, time and city. Jeolgi corrects for daylight saving and longitude, finds the exact solar term, and shows all four pillars with the reasoning visible.
Gapja — Korean Saju reading
Gapja reads the chart Jeolgi builds: day master, five elements, ten gods, ten-year luck cycles, and compatibility, written for people who have never seen a Saju table.
Start here
- What is Saju? The Korean Four Pillars system in one page: pillars, stems and branches, the day master, and why the month changes on a solar term rather than the first of the month.
- How a Saju calculator works — the six steps between a birth certificate and a chart, and the two steps most free calculators skip.
- What a Saju reading tells you — and what a reading cannot tell you.
- Saju vs BaZi — the same calendar system under a Korean and a Chinese name, and where Korean practice differs.
- Why birth time and place matter — daylight saving time and longitude can move an hour pillar, and sometimes a day pillar.
Why a second Saju app
Most English-language Saju apps hand a birth date to a language model and print whatever comes back. The pillars are often wrong before the reading starts, because summer time was not removed, the birth city was ignored, or the month was switched on the calendar date instead of the solar term. 60Gapja separates the two jobs. The calculation is deterministic code that is tested against the Korean reference almanac used by professional readers. The interpretation runs on top of that chart and never touches the arithmetic.
60Gapja is based in Atlanta, Georgia. Both apps are in development for 2026, iPhone first. Contact: 60gapja.app@gmail.com.