Method
Saju follows the sun and the seasons, not your wall clock.
Here is exactly what we do with the three things you enter, and the conventions we chose where schools differ.
What Saju is
Saju (四柱, “four pillars”) is Korea's birth-chart tradition. Your year, month, day and hour of birth each become a pair of characters, a Heavenly Stem over an Earthly Branch. The eight characters describe how the five elements (Wood, Fire, Earth, Metal, Water) move through your life. The Day stem is the Day Master, the character that stands for you.
Your clock time becomes a single instant
Your birth date, time and city are combined with the IANA timezone database, so the daylight-saving rule in force in that city, in that year, is applied. The result is one instant in UTC.
Year and Month pillars use the exact solar-term instant
The Korean and Chinese calendars change year at 입춘 (立春, “start of spring”) and change month at each of the twelve 節 terms. These are astronomical moments — the sun reaching a given ecliptic longitude — and they happen at the same instant everywhere on Earth. We compare your UTC instant with the term table in its reference frame (UTC+8) and warn you if you were born within 24 hours of a boundary.
Day and Hour pillars use true solar time at your birthplace
The twelve two-hour “animal hours” are defined by the sun: 午 (Horse) is centred on local solar noon. We shift your instant by your longitude (4 minutes per degree) and by the equation of time (the sun runs up to 16 minutes fast or 14 minutes slow across the year). A 12:00 birth in New York is a 10:59 solar birth — a 巳 hour, not 午. Near midnight this can also move your Day pillar.
The 23:00–01:00 hour (子時)
We follow the common Korean convention: a birth between 23:00 and 24:00 solar time keeps that day's Day pillar and takes the next cycle's 子 hour stem. Some schools advance the day; we state our rule so you can compare.
Unknown birth time
We never guess noon. If you don't know your hour, we compute three pillars and say so on the card and in any report.
Ten Gods, elements and luck cycles
Ten Gods are derived from the element and polarity relation between each stem and your Day Master: the element you produce, the element you control, the one that controls you, the one that produces you, and your own. The element bars weight visible stems and the main hidden stem at 1.0, and secondary hidden stems at 0.5 and 0.3. Ten-year luck cycles (대운) start at the age set by the distance to the nearest solar term and run forward or backward according to the classical rule based on year-stem polarity and gender.
What this is not
SajuDecoded is a tool for reflection. It does not predict events and it is not medical, legal, financial or psychological advice. If a reading ever makes you feel worse instead of clearer, please close it and talk to someone you trust.