Birthdays, festivals and almanacs often raise the question "what's the lunar date today?" Here are the basic rules.
What kind of calendar is it?
The Chinese "farmers' calendar" is a lunisolar calendar. It follows:
- The moon: a month runs from one new moon to the next, about 29.5 days on average.
- The sun: the 24 solar terms follow the sun's position on the ecliptic, tracking the seasons.
The Gregorian calendar follows only the sun and purely lunar calendars such as the Islamic calendar only the moon; the Chinese calendar combines both.
How dates are set
Day one: the day containing the new moon — when the moon is between sun and earth and nearly invisible — is the 1st. So the moon is barely seen around the 1st and is fullest around the 15th–16th.
Long and short months: since a lunation is about 29.5 days, months have 30 or 29 days, determined by astronomical calculation rather than strict alternation.
Leap months: twelve lunar months total about 354 days, some 11 days short of a solar year. To stay aligned with the seasons, a leap month is added roughly every two to three years — usually seven in nineteen years. Traditionally the leap falls on a month containing no "principal term" (zhongqi).
Reference time: the calendar is computed for UTC+8, Beijing time. China's 2017 national standard GB/T 33661—2017 codifies this along with rules for new moons, solar terms and leap months. Abroad, your local date can differ by one day.
Reading lunar dates
- Months: First (Zheng) month, Second… Tenth, Winter (11th) month, La (12th) month; leap months are "leap X month".
- Days: chu yi to chu shi (1–10), shi yi to er shi (11–20), nian yi (21) to nian jiu (29), san shi (30).
- Years: named by stem-branch — after New Year 2026 it is Bing Wu, after New Year 2027 Ding Wei.
Many calendars also show the stem-branch day, e.g. Xin You — a sixty-day cycle unbroken since antiquity and unaffected by month lengths or leap months.
Solar terms and lunar dates
Solar terms follow the sun, so their Gregorian dates are fairly fixed — Lichun around 3–5 February, the winter solstice around 21–23 December — while their lunar dates shift a lot. Likewise Chinese New Year (lunar 1st of the 1st month) falls between about 21 January and 20 February.
Tips
- Check your time zone; convert to Beijing time if needed.
- Note whether this year has a leap month.
- If your lunar birthday is in a leap month that doesn't exist this year, people usually celebrate in the regular month of the same name.
- Look up stem-branch day, solar terms and almanac info together if useful.
Summary
Lunar dates start on the new moon, use 29- or 30-day months by astronomy, add leap months to stay with the seasons, and are computed for Beijing time. For cultural reference only.
This article is for cultural reference only and is not advice for any decision.