How Zi Wei Dou Shu Schools Handle Leap Months

A leap month is a defined calendrical interval, but Zi Wei Dou Shu traditions do not all map it into chart rules identically.

Common method types

• Preserve the leap month: use a school-specific table.
• Treat it like the regular month: no separate leap handling.
• Split the month: assign early and late portions differently.
• Convert first: verify the Gregorian date, then apply an engine rule.

Why charts differ

A changed month assignment can alter palace placement and later calculations. This may be a rule difference rather than a software defect.

Comparison steps

1. Verify the leap month in a reliable calendar.
2. Preserve the original leap notation.
3. Document each tool’s rule.
4. Compare implementations only under the same rule.
5. Disclose school differences.

Worked case: one record, three rule tests

Suppose a certificate records “twelfth day of the leap fourth month.” Do not erase the word “leap.” First identify the Gregorian year and confirm the exact start and end dates of that year’s leap fourth month in an authoritative calendar. Then create three test copies: one retaining explicit leap-month status, one treating the period as an extension of the named month, and one applying the dividing-day rule of a specified school.

Practical software checklist

1. Select the calendar actually used by the record.
2. For a lunar entry, use an explicit leap-month control; never add a month manually.
3. Write down the Gregorian date returned by the conversion.
4. Cross-check that date with a second reliable calendar source.
5. Compare palaces and stars only after both tools agree on the date.

Two kinds of claims that must remain separate

Whether a year contained a leap month is a verifiable calendrical fact. How a Zi Wei Dou Shu school uses that month is an interpretive convention. The first belongs to astronomical calendar tables; the second must be declared by the practitioner or software. Treating a school rule as astronomy—or excusing a wrong calendar conversion as a school difference—makes an audit impossible.

Practical questions

Can I enter the leap month as the following numbered month?

No. A leap fourth month is not a fifth month. Preserve the recorded lunar designation and use a conversion that explicitly represents leap status.

What if the software has no leap-month control?

Do not guess. Convert the source through a reliable calendrical tool, save the resulting Gregorian date, and check the chart software’s documentation. If its internal rule is undisclosed, record that limitation when comparing results.

Can life events determine the correct leap-month school?

Retrospective narrative fit cannot establish a calendar convention. It is prone to selective matching. Choose or compare schools transparently, keep the same source data, and avoid rewriting the date until an interpretation feels accurate.

Conclusion

Separate calendrical fact from interpretive convention. Transparent rules matter more than claiming one universal answer. Keep the original lunar wording beside the converted date so future software changes remain auditable.