What does the calculator use?
The required inputs are birth date, birth time, country, city, time accuracy, and an optional sex-at-birth field used only by the disclosed traditional Da Yun direction rule. Location resolves the historical timezone and longitude. Unresolved or uncertain inputs reduce the displayed precision instead of being silently guessed.
Which calculation conventions are active?
- Gregorian and lunar input are normalized to a Gregorian instant before pillar calculation.
- The Year Pillar uses the site's documented Li Chun convention.
- The Month Pillar changes at exact Jie boundaries.
- The primary birth clock uses apparent solar time and compares it with historical local civil time.
- The adopted Zi-hour day boundary begins at 23:00.
- Da Yun direction uses birth-year stem polarity plus the optional sex-at-birth input.
- Da Yun start uses the previous or next exact Jie with the versioned minute-conversion rule.
Which libraries and cross-checks are used?
The calculation layer uses Astronomy Engine for astronomical timing and lunar-javascript for calendar and sexagenary-cycle cross-checks. The production dependency versions are recorded with the deployed code.
What boundary cases are tested?
The automated suite covers Li Chun and exact Jie changes, the 23:00 Zi-hour boundary, historical daylight-saving conversion, unresolved locations, unknown birth times, apparent-solar-time changes across hour or day boundaries, Southern Hemisphere timezone handling, lunar-input normalization, luck-cycle direction, and solar-term cross-checks.
Two reproducible reference cases
Wuhan reference: 11 November 1994 at 12:00, Wuhan, using the active convention, produces Year 甲戌, Month 乙亥, Day 辛丑, Hour 甲午.
Jing Zhe boundary: for Wuhan on 5 March 2024, the tested moment before the exact Jie remains in Month 丙寅 and the tested moment after it changes to 丁卯. The purpose is to verify the boundary behavior, not to make an event prediction.
Why can another calculator disagree?
Differences can result from historical timezone data, daylight-saving handling, local civil time versus true solar time, Li Chun or Lunar New Year year boundaries, exact versus date-only solar terms, Zi-hour conventions, Da Yun direction rules, and rounding or display conventions. A disagreement should be resolved by comparing methods before interpreting the chart.
What does this method not prove?
BaZi is a traditional interpretive framework. A reproducible chart calculation does not scientifically validate a symbolic interpretation, diagnose a condition, or guarantee future health, wealth, love, career, or safety outcomes.
Calculation layer: calculation-layer-v5
Convention: bazi-horosa-primary-v1
Last reviewed: September 23, 2026