PRACTICAL CONVERSION GUIDE
A Lunar Birthday in a Leap Month: Which Date Do You Use?
In 2025, lunar month 6 began on June 25. Leap month 6 began on July 25. A birthday recorded simply as “6/1” is missing a detail you need before planning a celebration.
By China Converters · Published
First establish which date the birth record means
If you know the Gregorian birth date, enter that complete date in the lunar birthday planner. It returns the lunar year, month, day and leap-month status. Keep all four pieces together.
If the record already gives a lunar date, look for 闰 before the month number. 闰六月 means leap month 6. It is a second occurrence of that lunar month number, not February 29 and not another name for the regular sixth month. Check the original birth year as well: a leap-month entry must exist in that year's calendar.
A family note such as 六月初一 means the first day of the sixth lunar month, but it may not say whether a leap month was intended. If the year contains both, check the original Gregorian date, a fuller record or the family member who supplied it before filling in the gap.
Check both sixth months in the 2025 table
The Hong Kong Observatory's 2025 table gives these two conversions:
- Regular lunar 2025/6/1 → Gregorian 2025-06-25.
- Leap lunar 2025/6/1 → Gregorian 2025-07-25.
To check them in the planner, choose lunar input, year 2025, month 6 and day 1. Switching the leap-month checkbox changes the original Gregorian date from June 25 to July 25. Use a search start date on or after the entered birth date.
That establishes the birth date. Deciding which future occurrence to celebrate is the next step, especially in a year without a matching leap month.
Agree on the birthday convention
For someone born in leap month 6, ask what happens when a year has no leap month 6. Does the family celebrate in regular month 6, wait for another matching leap month, or follow another custom? The planner makes the available choices explicit:
| Choice | What to include | Consequence |
|---|---|---|
| Prefer leap month | The matching leap month if present; regular month otherwise | The Gregorian date follows that stated fallback |
| Regular month every year | The regular occurrence of that month and day | A leap occurrence is not additionally selected |
| Both occurrences | Regular and matching leap occurrences when both exist | One year can contribute more than one listed date |
| Leap month only | Only a matching leap-month occurrence | Many years contribute no birthday date |
To compare the settings, enter lunar birth year 1987, month 6, day 1 with the leap flag selected, and search from 2025-01-01. “Regular month every year” starts with June 25, 2025; “prefer leap month” starts with July 25; “both” includes both dates. “Leap month only” starts with the July date and leaves years without a matching leap month out of the list.
Move the search start past June 25 and that earlier regular occurrence disappears from the upcoming list. Keep the start date with the policy when comparing results, then use the settings that match the family's practice.
If the original birthday falls on day 30
Lunar months can have 29 or 30 days. A birthday on day 30 therefore creates a second decision: what should happen when the target month ends on day 29?
The planner offers two choices. Skip that occurrence, or use the target month's last day and mark the result as adjusted. Keep this choice separate from the leap-month convention. For example: “Use the regular sixth month each year; when day 30 is missing, celebrate on day 29.” That is enough information for another person to reproduce the dates.
Check adjusted entries before sending invitations or saving reminders. The original birth date stays unchanged; the adjustment applies to the chosen celebration date.
Save individual dates, not a yearly July reminder
After checking the results, download the .ics file and inspect the imported events in your calendar. The planner exports separate all-day occurrences. A yearly Gregorian recurrence on July 25 would keep repeating July 25; it would not recalculate leap lunar 6/1.
“Next five occurrences” also differs from “next five years.” Selecting both regular and leap dates can add two events in one year. Selecting leap-only can leave a gap of years. If the supported calendar window ends before five dates are found, keep the shorter result instead of treating it as a full five-date schedule.
The export contains event dates and lunar labels, without the original birth date or age. Review it before sharing if you want to keep a celebration schedule private.
When to check another record
This site's tools accept Gregorian dates from 1901 through 2099. They work with dates, not birth times or time-zone conversions. If a record near midnight gives a conflicting date, preserve the record and investigate its time and calendar convention separately.
The Observatory also notes possible one-day differences for some far-future dates near midnight. Use its table for the year you are planning, and see the site's calendar limitations before relying on a distant result.
References
- Hong Kong Observatory: Gregorian–lunar conversion table for 2025 (PDF) — The regular and leap sixth-month dates in the worked example.
- Hong Kong Observatory: calendar conversion tables and limitations — Year-by-year calendar tables and the Observatory's explanation of far-future date uncertainty.
References checked 2026-10-26.