How to use it
- Gregorian → lunar: pick a date (today by default) to get the lunar month and day, the stem-branch year and zodiac animal, and the solar term if one falls that day.
- Lunar → Gregorian: choose the lunar year, month and day. If that year has a leap month of the same number, the "Leap month" box becomes available.
- Lunar birthday: choose the lunar month and day of the birthday to list the matching Gregorian dates for several years from now. The ordinary (non-leap) month is used.
- Solar terms: choose a year to list the dates of its 24 solar terms.
How the lunar calendar works
Where the data comes from
The Chinese calendar is lunisolar: each month begins at the new moon and has 29 or 30 days, and a leap month is added roughly every two or three years to keep it in step with the seasons. Month boundaries and leap months come from astronomical calculation rather than a simple formula, so the tool does not compute them itself. It uses the Hong Kong Observatory's Gregorian–lunar conversion tables, from which the first day of every lunar month, the leap months and the solar terms for 1901 to 2100 were extracted and then checked against the original tables day by day — more than 70,000 days, all matching.
Leap months and month lengths
A leap month follows the month with the same number: 2025 has a leap sixth month running from 25 July to 22 August, 29 days. Whether a month is long or short changes every year; the twelfth month of both 2025 and 2026 has only 29 days, so neither year has a "twelfth month, 30th day", and New Year's Eve is the 29th. People born on the 30th therefore celebrate on the 29th in some years, and the tool marks those years.
Stem-branch years and zodiac
The sexagenary (stem-branch) cycle repeats every sixty years. The tool changes year at Chinese New Year: from 17 February 2026 it is the bing-wu year of the Horse, while the day before is still the yi-si year of the Snake. Some traditions, notably in fortune-telling, change year at the solar term Lichun (Start of Spring) instead, which usually falls within a few days of New Year; on 4 February 2024, for example, it was Lichun but still the 25th day of the twelfth month of the year of the Rabbit.
The 24 solar terms
Solar terms mark the sun's position along the ecliptic, so their Gregorian dates hardly move — two a month, varying by a day or so. Qingming was 4 April in 2025 and 5 April in 2026. On the lunar calendar, by contrast, they fall on very different days from year to year. The dates also come from the Hong Kong Observatory tables.
Examples
| Query | Result |
|---|---|
| 30 September 2026 | Eighth month, day 20, year of the Horse |
| 17 February 2026 | First month, day 1 (Chinese New Year) |
| Lunar 2026, eighth month, day 15 | 25 September 2026 (Mid-Autumn Festival) |
| Lunar 2025, leap sixth month, day 1 | 25 July 2025 |
| Lunar birthday 8/15, three years from 2026 | 25 Sep 2026, 15 Sep 2027, 3 Oct 2028 |
Someone born on the 30th day of the twelfth month: in 2025 and 2026 that month has only 29 days, giving 16 February 2026 and 5 February 2027 — New Year's Eve both times.
Limits
- Covers 19 February 1901 to 8 February 2100 — lunar years 1901 to 2099.
- Lunar dates follow UTC+8 (China and Hong Kong time), as in the Observatory's tables; for births elsewhere the local date may differ by a day.
- The zodiac changes at Chinese New Year; traditions that change at Lichun differ for a few days.
- Almanac content such as auspicious days is not provided.
Frequently asked questions
Why does a lunar birthday move around the Gregorian calendar?
A lunar year is about 11 days shorter than a Gregorian one and is realigned with leap months, so the same lunar date shifts by days or weeks from year to year.
What about people born in a leap month?
The birthday lookup uses the ordinary month with the same number. Leap months do not occur every year, and families handle this differently.
What if the birthday is on the 30th and this year has no 30th?
In a 29-day month the tool uses the 29th, the last day of the month, and marks it in the table.
Does the zodiac year start at Chinese New Year or Lichun?
This tool uses Chinese New Year, the everyday convention; some traditions use Lichun.
What date range is covered?
Lunar years 1901 to 2099: 19 February 1901 to 8 February 2100.