BaZi Methodology
Exactly how our BaZi engine calculates — every conversion step, every convention we follow, and where interpretation begins.
Deterministic calculations are independently validated (736 assertions + 50 public cases). Interpretive layers follow the stated classical methodology below and may vary between schools.
1. The Calculation Pipeline
Every step is deterministic and locked by tests in our Engine Validation suite.
1
Clock time recorded Input
The time written on the birth certificate — in the local civil time of that place and date.
2
Historical DST reversed L1 · 37 cases
If the birth date fell in a daylight-saving period (US, EU, UK, Australia, China 1986–91), one hour is subtracted to recover standard time.
3
Timezone normalized L1
Civil time converted to the zone’s standard offset (e.g. UTC+8 for Beijing).
4
Longitude correction L1
Cities east/west of the timezone’s central meridian gain/lose 4 minutes per degree. Kashgar (75.99°E) shifts −176 minutes.
5
Equation of Time L1
Earth’s orbital eccentricity adds up to ±16 minutes depending on the day of year.
6
True Solar Time L1 · edge-tested
Steps 3–5 combined: the sun’s actual position at the birthplace. This can roll the clock back or forward across midnight.
7
Hour pillar (Shi Chen) L2 · 6 cases
True solar time mapped to the twelve 2-hour branches. Near-boundary births trigger a warning.
8
Solar-term check (minute precision) L1 · 68 cases
Year and month pillars switch at the exact minute of Li Chun and each Jie term — VSOP87 solar model, not calendar-day approximations.
9
Day pillar L1 · 414 cases
Jia-Zi anchor verified by three independent algorithms across 1900–2100.
10
Hidden stems & Ten Gods L3 · 100-cell matrix
Each branch expanded into its hidden stems (principal 1.0 / middle 0.6 / residual 0.4); Ten Gods derived per Day Master.
2. Conventions We Follow
Where schools differ, we publish which convention we use, why, and who else uses it — so you can compare apples to apples.
| Convention | Our Method | Why |
|---|
| Year boundary | Exact minute of Li Chun (立春) | The classical Zi-Ping rule; calendar-day approximations misclassify births within ~1 day of the boundary. |
| Month boundary | Exact minute of each Jie term | Same logic — the month pillar follows solar terms, not lunar months or calendar months. |
| Midnight (Zi-hour) | Late-Zi school: 23:00–24:00 keeps the current day’s pillar; hour stem derives from that day’s stem | Matches Yuan Heng Li Zhen and Wen Zhen BaZi, the two most widely referenced professional engines. |
| Hidden-stem weights | Principal 1.0 · Middle 0.6 · Residual 0.4 — not normalized | Tian-gan si-zhu (pure branches) vs mixed-storehouse branches differ qualitatively; normalization erases weak residual roots that matter for Yong Shen. |
| Life Palace | San Ming Tong Hui method with post-Zhong-Qi advance | Classical source text; verified against a 144-cell reference table. |
| Shen Sha lookup | Day branch AND year branch both act as anchors for horse/flower/hat/cloud; day stem for Tianyi/Wenchang | Dual-anchor is the mainstream professional reading; single-anchor misses roughly half of activated stars. |
2.5 Interpretation Layer — Rules Under Test
The interpretive rules below are not free-form AI text. Each is a deterministic scoring rule with a published case in our regression suite — if a future change breaks one, deployment is blocked.
| Rule | Scoring | Verified Case |
|---|
| In Season (得令) | Day Master in its Wang month: +3 · Xiang: +2 · Xiu: −1 · Qiu: −1 · Si: −2 | Case: Geng metal born in You month → +3 (In Season, Wang), contributes to Strong verdict |
| Peer rooting (得地) | Day Branch hidden stem = peer element: +0.5 · resource element: +0.3 | Case: Bing-Wu day — Wu hides Ding (peer) → +0.5 |
| Network power (得势) | Year/Month/Hour stem = peer: +1.0 · resource: +0.7 | Applied in every chart; factors are itemized in the Strength Factors list |
| Strength thresholds (4-pillar) | Very Strong ≥ 6 · Strong ≥ 3 · Neutral ≥ 1 · Weak ≥ −1 · Very Weak < −1 | Case: Geng/You chart scores 4.9 → Strong |
| Strength thresholds (3-pillar) | Hour contributions absent → thresholds soften: Very Strong ≥ 4.5 · Strong ≥ 1.5 | Case: hour-unknown Geng/You chart scores 4.4 → still Strong under softened threshold |
| Yong Shen direction | Strong chart → favorable = Officer/Output/Wealth (克泄耗); Weak chart → favorable = Resource/Peer (生扶) | Case: Strong Geng chart → favorable includes Huo(官杀); unfavorable includes Jin(比劫) |
| Pattern: Jian Lu (建禄格) | Day Master born in its Lu month | Case: Jia day in Yin month → Jian Lu |
| Pattern: Yang Ren (羊刃格) | Day Master born in its Blade month | Case: Geng day in You month → Yang Ren |
| Self-Punishment (自刑) | Same branch appears twice: Chen-Chen / Wu-Wu / You-You / Hai-Hai | Case: double You chart → Self-Punishment card triggered |
Each rule is a deterministic scoring function exercised by test_interpretation.js in our regression suite — the reasoning chain you see in your report is reproducible, not invented.
3. Where Calculation Ends and Interpretation Begins
Deterministic layer (fully validated). Everything in section 1 is astronomy and arithmetic — two independent engines must agree on every pillar, and 50 public cases let you reproduce the results in your own browser.
Interpretive layer (methodology-stated). Strength verdicts, patterns, favorable elements and period readings follow the stated classical methodology above. Honest practitioners can and do disagree here — different schools weight the same chart differently. We publish exactly which rules we use so you can judge, compare, or override.
