Solar, Lunar, and Leap-Month Dates
Date input is one of the most common sources of chart errors. Solar normally refers to the Gregorian calendar, while the lunar calendar is the traditional lunisolar calendar. Their year, month, and day numbers cannot be used interchangeably. If “the fifteenth day of the eighth month” came from a lunar record, the lunar option must be selected rather than entering the same numbers as a Gregorian date.
Confirm the original record
The most reliable information usually comes from a birth certificate, hospital record, or a record made by the family at the time. When asking relatives, confirm whether the date is Gregorian or lunar, whether the time is AM or PM, and whether it was close to midnight. Avoid relying only on a vague memory many years later.
Why leap months matter
The lunar calendar inserts a leap month in some years to coordinate months with the solar year. A leap month is not the same month as the regular month with the same name. If the record says “leap fourth month,” the leap-month option must be selected. Omitting it may change the converted Gregorian date and chart structure.
Midnight and time boundaries
Births near 23:00, 00:00, or a traditional two-hour boundary may produce different results under different day-change rules or schools. Keep the original minutes and document which rule is used. If only an approximate time is known, acknowledge the uncertainty instead of presenting false precision.
Input checklist
- Confirm Gregorian or lunar calendar.
- Check whether a lunar date is in a leap month.
- Confirm AM, PM, and minutes.
- Confirm the time zone used at the birthplace and date.
- Record whether true solar time is applied.
- Compare methods when the time is close to a boundary.
Example: “eighth day of the fourth month” is insufficient
The record still needs a year, calendar type, leap-month status, AM or PM, and birthplace. Find the original record, convert independently, and cross-check against season, festival, or hospital evidence.
Troubleshooting order
- Check calendar and leap month.
- Check 12/24-hour format and AM/PM.
- Check midnight and hour boundaries.
- Only then compare solar-time and school rules.
Site test: cross-checking solar and lunar input paths
We first generate a chart through the solar-date path and transcribe the displayed lunar date. We then enter that lunar date through the lunar path and confirm that the returned solar date matches. A leap month requires the separate leap-month control. The Hong Kong Observatory conversion tables provide an independent calendrical check.
| Source record | Correct path | Still required |
|---|---|---|
| 1990-06-15 | Solar/Gregorian | Birth time and place |
| Lunar year, month, and day | Lunar | Leap-month status |
| “Fourth month, day 23” | Not yet determinable | Year, calendar, and leap status |
How to document a conversion disagreement
Save the original wording, each tool’s input mode, returned date, version, and leap-month setting. Establish the calendar fact with an authoritative table before comparing Zi Wei Dou Shu conventions. Do not choose a date because the resulting interpretation seems more personally accurate.
Conclusion
A calendar error changes a chart earlier and more completely than most interpretation differences. Preserve the source record, conversion, and rule set. Save both the original wording and converted date so another reader can reproduce the choice later.
Sources and editorial note
Updated August 10, 2026. Solar-lunar verification uses the Hong Kong Observatory calendar material, calendrical concepts from the Chinese Astronomical Ephemeris, and bidirectional tests of this site’s iztro 2.5.8 input paths. School-specific leap-month rules are covered separately. See our editorial and testing standard.