Methodology

How BaziTrace calculates a chart

BaziTrace uses a deterministic calculation: the same inputs produce the same chart. This page explains the conventions behind that result and where other Bazi systems may differ.

Read the boundaries before interpreting a chart. The four pillars come from the reference library lunar-typescript 1.8.6 (MIT), which handles the solar-term ephemeris and the day-boundary convention internally. We do not resolve the birth city into a time zone, longitude, historical time zone, or true solar time.

Inputs and outputs

Inputs
Gregorian date, 24-hour civil time, and an optional city name
Outputs
Year, month, day, optional hour pillar · day master · five-element tally · boundary notes
Hidden stems
Not included in the five-element tally
Da-yun and special stars
Not included

Conventions used

  1. Reference library. Year, month, day, and hour pillars are produced by lunar-typescript 1.8.6 using sect 2 (late Zi 23:00–23:59 keeps the day pillar on the current day). 30/30 agreement on the published boundary matrix.
  2. Civil time. The entered time is treated as the user's local civil time. Birth city is shown for reference but does not change the chart.
  3. Year pillar. Changes at the precise moment of 立春, per the reference library.
  4. Month pillar. Changes at the precise moment of the corresponding solar term, per the reference library.
  5. Day pillar. The 60-day sexagenary cycle; the day boundary follows sect 2 of the reference library (late Zi stays on the same day).
  6. Hour pillar. 子时 spans 23:00–00:59 of the next day; the day pillar above stays on the current day for the late-Zi window.
  7. Five elements. Each visible stem and branch contributes one count. The total is eight with an hour pillar and six without one.

What this engine still does not do

  • It does not look up a longitude or time zone for the birth city. The entered time is used as local civil time.
  • It does not apply historical time zones or daylight-saving transitions. Births before or around DST changes may need a separate civil-time conversion the user must supply.
  • It does not apply true solar time. A chart near the east or west edge of a time zone may read 10–20 minutes earlier or later than a true-solar-time engine would.
  • It does not include hidden stems inside branches in the five-element tally.

These are calculation conventions, not bugs. BaziTrace shows its method so you can compare results on the same basis. Use the chart for cultural learning and personal reflection, not for medical, legal, financial, or other professional decisions.

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