About SajuHub
Last updated October 7, 2026
SajuHub is an English guide to Korean Saju (사주) — the Four Pillars of Destiny as it is practiced in Korea. We start with one thing done carefully: a free calculator that turns your birth moment into your eight characters, saju palja (사주팔자), and shows every step of the math.
Why did we build another Saju calculator?
Before writing a line of code we reviewed 27 English Saju and Bazi calculators. Several ask you to tick a daylight-saving box yourself; others never ask where you were born. We could not find one that clearly looks up the historic clock rules for your birthplace. That is easy to get wrong — and an hour’s error can change your hour pillar, or, near midnight, even your Day Master. So on SajuHub you just pick your birth city. We look up the clock rules that were in force in that city on that date, correct for its longitude, and show you exactly what we did.
How do we calculate your Four Pillars?
- Year and month pillars change at the solar terms — the year at Ipchun (立春), Start of Spring — not on January 1 or the lunar new year. We compute each term to the minute from VSOP87 planetary theory (Bretagnon & Francou), following Jean Meeus, Astronomical Algorithms.
- Your birth time is converted to Universal Time (UTC) using the IANA time-zone database, which records historic daylight saving and time-zone changes for every region, including Korea’s 1987–88 summer time.
- Day and hour pillars follow local solar time: we shift the clock by four minutes for every degree of longitude between your birth city and its time-zone meridian. This longitude correction is standard practice in Korean almanacs (만세력). You can switch it off in the options.
- Korean lunar dates are converted with calendar data published by the Korea Astronomy and Space Science Institute.
- Birth cities come from GeoNames (CC BY 4.0) — more than 34,000 places with their coordinates and time zones.
The calculator covers births from 1900 to 2050. Everything runs in your browser; see our Privacy Policy.
How do we check that it is accurate?
We test the engine in three ways:
- Against an independent library we did not write: 3,000 random charts compared with the open-source almanac library lunar-python (6tail) — no differences in any of the eight characters. Its 1,812 solar-term moments match ours to within one minute.
- Against a second calculation of our own, built separately on Python’s standard time-zone library: more than 6,000 charts, including month ends, the edges of the 1900–2050 range, the late Rat hour and lunar dates — no differences.
- Against the almanac table of our Korean-language calendar tool: 700 random Korean births — no differences.
We re-run these checks whenever we change the engine. If you find a chart that looks wrong, please tell us — include the date, time and city, and we will look into it.
How are the readings written?
The interpretations on SajuHub are fixed texts we write ourselves for each Day Master and element pattern, drawing on the standard Korean meanings of the stems and branches. They are not generated on the fly for each visitor.
Saju describes tendencies and seasons, not fixed outcomes. Everything on SajuHub is for entertainment and self-reflection only. We do not make predictions about health, illness, money or legal matters, and nothing here is professional advice.
Who runs SajuHub?
SajuHub is made by Forecast (포캐스트), a small independent studio in Seoul, South Korea, that also builds free everyday web tools. Questions, corrections and ideas are welcome at ichingcho@gmail.com or on our contact page.