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A Chinese lunar month ending on day 29 has no day 30. If that month and day are the original birthday conditions, an exact date may therefore be unavailable in a selected search window. The useful response is to identify the reason, not silently change day 30 to day 29 and present the replacement as the original birthday.
Check the month before checking the day
Start with the month number and leap-month flag. If the record refers to an ordinary month, searching a leap month with the same number changes the birthday conditions. If it refers to a leap month, first check whether that month exists in the target window. Only then ask whether it has 29 or 30 days. These are separate causes of a missing match.
Use a calendar to inspect the boundary
Find the first day of the intended Chinese lunar month and the first day of the following actual lunar month. The date immediately before that second boundary shows whether the original month ends on day 29 or day 30. Do not use the last cell of a Gregorian month as a shortcut: Gregorian and Chinese lunar month boundaries do not coincide. You may need to view adjoining calendar months.
Remember what the target year means
The birthday finder searches a Gregorian year, from January through December. A lunar date belongs to a numeric lunar year as well, and the two annual windows start on different days. Read the complete candidate date and year label. A missing result should be investigated using the actual month, day, leap status and range, rather than assuming every Gregorian year must contain exactly one match.
Discuss a replacement celebration openly
Some families may choose the final day of the month, the following day, a fixed Gregorian birthday or a convenient gathering date. This guide does not prescribe any of those choices as a universal custom. Record the reason and the agreed date separately. For example, a note can say that the original lunar month lacks day 30 and the family chose its last day for this year's celebration.
Preserve enough information to repeat the check
Keep the original birthday, the target Gregorian year, whether the month exists, whether day 30 exists, and the celebration decision. If only a month and day are known, that may support an annual search but it does not establish the unique historical birth date. A complete Gregorian birth record can instead be checked through the date converter.
Treat unsupported dates differently
The verified Chinese lunar range is 1950–2035. An out-of-range message, incomplete input and a genuinely missing day are different outcomes. Use the lunar birthday finder after checking the input. If it produces two valid candidates rather than none, the two-occurrences guide explains why a Gregorian year can span matching dates from different lunar years.