Your birth details go to a fixed calculation engine. It uses the date, the time when known, the country’s time zone, a representative longitude and the selected gender setting. The writing AI receives the finished chart; it does not decide what the pillars should be.
How Hello Saju calculates your chart
- Validate civil birth information. The service checks the date, time confidence, time zone and coordinates.
- Apply the selected country’s time zone. Each supported country currently has one main IANA time zone.
- Apply true-solar-time correction. When a longitude is present, the engine adjusts clock time using longitude and astronomical timing data.
- Determine the pillars. The engine calculates year, month, day and hour stems and branches using the solar-term calendar.
- Derive chart relationships. It returns the Day Master, elemental associations, Ten Gods, hidden stems, interactions and luck-cycle data.
- Write the reading. The AI receives the structured chart and product instructions. It must interpret the supplied data rather than recalculate it.
Inputs used by this service
| Input | How it is used | Important limitation |
|---|---|---|
| Birth date | Calendar position and year, month and day pillars | Calendar conventions can differ between schools |
| Birth time | Hour pillar and time-dependent details | Unknown times are handled as uncertainty, not a default |
| Country | Main time zone and representative coordinate | It is not an exact birthplace |
| Longitude | True-solar-time adjustment | Country-level longitude is an approximation |
| Gender setting | Directionality used in luck-cycle calculation | Traditional conventions are binary and differ by school |
Our published calculation conventions
Day boundary: midnight
Hello Saju treats 00:00 as the beginning of a new civil day. Some Four Pillars schools treat the late Zi period around 23:00 differently, so charts near midnight can differ across calculators.
Country-level place data
The order form asks for country rather than city. The service uses that country’s configured main time zone and a representative coordinate. This makes ordering simpler for an international audience but means true-solar correction is approximate. A person born far from the representative longitude may receive a different hour pillar than an exact-city calculation near a boundary.
Element display
The visible element tally counts the primary elemental association of each pillar’s stem and branch. It is a readable summary, not a complete weighted judgment of element strength.
Engine and verification
The production calculator uses the versioned @openfate/bazi-engine 1.1.2. Our automated suite compares known civil-time fixtures, boundary behavior, solar terms, leap dates, daylight-saving cases, true-solar adjustment and deterministic luck-cycle ordering. Tests reduce software errors; they do not prove a divinatory interpretation scientifically true.
Why another calculator may disagree
There is no single settings panel shared by every Saju school. One calculator may change the day at 23:00 while another waits until midnight. They may also differ on solar-term boundaries, local solar correction, the direction and starting age of luck cycles, or the weight given to hidden stems.
Those choices rarely matter for an ordinary midday birth, but they can matter a great deal near midnight, a two-hour branch boundary or a solar term. Distance from the representative country coordinate adds another reason to read a boundary case cautiously.