Gregorian to Lunar Date Calculator

To express a solar calendar date in lunar terms, you need the lunar year boundary (Lunar New Year), the length of each month that year, and any intercalary (leap) month. Professional calendars publish these tables decades in advance.

This calculator estimates lunar month and day by counting days from Lunar New Year for the inferred lunar year, using fixed 29-day month blocks. It identifies the correct lunar year for dates near January and February but month/day results are approximate.

Example: a Gregorian date in mid-August 2026 falls in lunar year 2026 several months after February’s Lunar New Year. For Mid-Autumn Festival planning, cross-check lunar month 8 day 15 against a trusted almanac — simplified math may miss the exact day.

The lunar year boundary is the first decision. A Gregorian date before Lunar New Year belongs to the previous lunar year — so January 15, 2026 is still lunar 2025, while February 20, 2026 is lunar 2026. Getting the year wrong shifts every subsequent month by one.

Month and day are then estimated by counting days from that Lunar New Year with fixed 29-day blocks. Real months alternate irregularly between 29 and 30 days, so the estimate can drift by a few days by late summer and by more in a leap year when an intercalary month is skipped entirely.

Festival dates are the cases where the approximation matters most. Mid-Autumn on month 8 day 15, Dragon Boat on month 5 day 5, and Double Ninth on month 9 day 9 should always be confirmed against a printed almanac or official calendar before travel or ceremony planning.

Day boundaries follow Chinese civil midnight conventions in most modern tables. Birth times late at night can occasionally be assigned to the next lunar day in traditional almanacs that use astronomical new-moon timing — another reason important personal dates deserve a specialised source.

Leap months (闰月) repeat a month number rather than inserting a thirteenth name. When an almanac shows a leap marker before the month, select that leap month explicitly; this tool's fixed-block estimate cannot place intercalary months correctly.

Midnight-to-midnight lunar date boundaries follow Chinese civil calendar conventions — if you were born late at night, some almanacs assign the next lunar day earlier than local clock time suggests.

Leap lunar months repeat an entire month name in some years — select leap month when almanacs show 闰 before the month label.