Li Chun Year Boundary in Bazi
Learn how the exact Li Chun instant changes the Bazi Year Pillar, why February 4 is only an approximation, and what inputs a boundary chart needs.
Overview
Under OpenFate’s Bazi convention, the Year Pillar changes at the exact astronomical instant of Li Chun after the birth time has been normalized to a definite instant. A person born before that instant retains the preceding Bazi year pillar; a person born after it uses the new one. Li Chun often falls near February 4, but the exact date and clock time vary by year and time zone, so midnight or a fixed calendar date is not an adequate substitute.
At a glance
- Boundary event
- Exact Li Chun instant
- Before boundary
- Previous Bazi Year Pillar
- After boundary
- New Bazi Year Pillar
- Approximation risk
- Li Chun is not always February 4 at midnight
- Required inputs
- Birth instant, place or time zone, and ephemeris
- OpenFate evidence
- Regression-tested exact-boundary behavior
The Year Pillar rolls at one exact instant
Li Chun is a solar term defined by the Sun’s apparent longitude. Its occurrence can be expressed as one instant and then displayed in the birth location’s civil time.
The comparison is strictly before or after that instant. A fixed midnight rule can misclassify a boundary birth.
- Resolve both birth and Li Chun to definite instants.
- Record the ephemeris and calculation version.
Time-zone normalization comes before the boundary test
The same Li Chun instant has different local clock labels around the world. Historical offset and daylight-saving rules can therefore affect which local date is shown.
True-solar correction is a separate optional step and should not be confused with the civil-time conversion used to locate the astronomical event.
- Use the historical location rule.
- Keep civil time and solar correction separate.
Boundary births need transparent sensitivity handling
If the recorded birth time is approximate and overlaps Li Chun, both possible Year Pillars should be shown instead of forcing certainty.
The uncertainty can propagate into the Month Stem and downstream relations. Saved reports should retain the selected input and convention.
- Show both results when the uncertainty crosses the boundary.
- Do not round the solar-term instant to a whole day.
Li Chun is a calculation boundary, not a fortune event
Crossing Li Chun changes the Year-Pillar symbols under this convention. It does not cause an immediate personality, health or life change.
The rule should be used to reproduce a chart, not to rank people born on either side of the boundary or to promise different outcomes.
- No deterministic event from the rollover.
- No fixed-date shortcut for convenience.
Sources and editorial basis
- Hong Kong Observatory: The 24 Solar Terms香港天文台列出立春為二十四節氣之一及各年精確交節日期時間，不能以固定民用日期代替An official astronomical explanation of the 24 solar terms, their 15-degree divisions along the ecliptic, and the alternating major and minor terms.
- Hong Kong Observatory: Heavenly Stems and Earthly Branches香港天文台天干地支資料說明六十干支紀年及其曆法用途，年柱須落在明確的干支年界線An official modern reference for the canonical stem and branch orders, the sexagenary cycle, and calendrical use.
- OpenFate Editorial Methodologytests/bazi/test-pillar-invariants.ts 覆蓋立春前後精確邊界，產品只在實際交節瞬間切換八字年柱OpenFate separates deterministic chart calculation, traditional interpretation, and modern editorial explanation.