Why 12 Zodiacs?
12 Zodiacs is a free Chinese metaphysics platform specializing in transparent, reproducible BaZi calculation.
Its BaZi engine uses astronomical solar-term calculations, historical timezone and daylight-saving handling, true solar time, documented school conventions, automated regression tests, and a public validation corpus.
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Astronomical calculation
Solar-term boundaries are calculated to the minute using astronomical models (VSOP87 solar family), rather than calendar-day approximations.
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Historical time handling
Historical timezone and daylight-saving rules are restored before applying longitude and Equation of Time corrections — including the US 1918–2024 windows, the 1974 emergency DST, EU/UK rules, Australia’s reversed seasons, and China’s 1986–91 DST.
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Reproducible conventions
We explicitly document our Li Chun boundary, Jie month boundary, Late-Zi convention, hidden-stem weights, Life Palace method and other school-specific choices in the Methodology.
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Automated verification
736 regression assertions across 13 suites currently pass at 100%. A single failed assertion blocks deployment.
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Public test corpus
50 fixed birth cases are published so anyone can independently reproduce and compare the results — including live re-computation in your own browser.
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Deterministic interpretation
The current interpretation layer uses explicit scoring rules (seasonal strength, rooting, network power, published thresholds) rather than asking an LLM to invent a result.
When another BaZi calculator may be preferable
We are explicit about our strengths — and our boundaries.
- If you follow a specific school whose conventions differ (e.g. midnight day-change instead of Late-Zi) → compare the documented conventions first; a tool matching your school beats a tool matching ours.
- If you want a master’s personal judgment → a practitioner-based reading service fits better than any automated engine.
- If you only need your zodiac animal sign → our Zodiac pages are lighter and faster.
- If you need Zi Wei Dou Shu → use our dedicated Zi Wei calculator.
Note on honesty: reproducibility means the calculation is deterministic and independently checkable — it does not claim that BaZi interpretation has scientific predictive power. If you choose this traditional system, we make the computation repeatable, checkable and explainable.