Gregorian and Chinese Calendars in Bazi
Learn how Gregorian dates and the Chinese lunisolar calendar represent birth dates, and why Bazi pillars still require solar-term and sexagenary rules.
Overview
Gregorian and Chinese calendars are two ways to label a date; neither label is itself a Four Pillars chart. A reliable Bazi calculator converts the recorded birth information into one definite instant, then applies the selected time-zone, solar-term, day-boundary and sexagenary-cycle rules. A lunar date can be a valid input after conversion, but its month number is not the Month Pillar and Lunar New Year is not automatically the Bazi year boundary.
At a glance
- Gregorian calendar
- Civil solar date representation
- Chinese calendar
- Lunisolar system with months, leap months and solar terms
- Bazi input
- One normalized instant plus location or time zone
- Year boundary
- OpenFate uses the exact Li Chun instant
- Month boundary
- OpenFate uses the twelve Jie instants
- Boundary
- A lunar month number is not a Month Pillar
The calendars label dates; the pillars classify an instant
The Gregorian calendar tracks civil dates in a solar system. The Chinese agricultural calendar combines lunar months with solar-season markers and may add a leap month.
Both can identify the same birth instant after a correct conversion. The Four Pillars are then calculated from that instant rather than copied from either date label.
- Keep the original recorded date.
- Store the converted instant and conversion direction.
Bazi year and month boundaries are separate rules
OpenFate changes the Year Pillar at the exact Li Chun instant and the Month Pillar at the exact twelve Jie boundaries. These are solar-longitude events.
Lunar New Year and the first day of a lunar month remain meaningful calendar dates, but they answer different questions and must not silently replace the declared Bazi convention.
- Name the year-boundary convention.
- Resolve the exact solar-term time for the relevant year.
Lunar input needs an unambiguous conversion
A lunar date must specify the calendar year, month, day and whether the month is leap. The place and local clock time are still needed for a birth chart.
After conversion, historical time-zone and daylight-saving rules are resolved before true-solar or pillar boundaries. A conversion result without provenance is difficult to reproduce.
- Preserve leap-month status.
- Do not assume today’s UTC offset for a historical birth.
Calendar choice is not interpretive evidence
Using a Gregorian or lunar input does not add an element, change personality or make a chart more traditional. Correctly converted inputs should identify the same instant.
Near a boundary, disclose uncertainty and compare plausible results instead of selecting the chart that produces the preferred reading.
- No symbolic meaning from input format.
- No hidden correction without disclosure.
Sources and editorial basis
- Hong Kong Observatory: The Chinese Agricultural Calendar香港天文台公曆與農曆對照表：同一日期可由兩種曆法標示，並列節氣及干支資料An official overview of how the Chinese agricultural calendar combines solar and lunar cycles, including months, leap months, and solar terms.
- Hong Kong Observatory: The 24 Solar Terms香港天文台二十四節氣資料：節氣以太陽視黃經位置界定，並提供精確交節時刻An official astronomical explanation of the 24 solar terms, their 15-degree divisions along the ecliptic, and the alternating major and minor terms.
- OpenFate Editorial Methodology產品先把出生地民用日期時間轉成同一時間點，再依時區、節氣與干支規則排四柱；曆名不作吉凶證據OpenFate separates deterministic chart calculation, traditional interpretation, and modern editorial explanation.