Calculate conversions between Gregorian and Chinese lunar dates in either direction, including leap months, zodiac and stem-branch years, and the next occurrence of a lunar date.

Convert a Gregorian calendar date.

Chinese civil-calendar dates: 1900-01-31–2101-01-28. Future month boundaries near midnight can differ by a day; verify important observances with an authoritative almanac.

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Lunar Calendar Formula

This calculator converts Gregorian dates and civil Chinese lunisolar dates using a fixed table of month lengths and leap months. There is no fixed day offset between these calendars.

S = S₀ + Σ Y + Σ M + (d - 1)
  • S is the Gregorian civil-day index; S_0 is the epoch Gregorian 1900-01-31, corresponding to lunar year 1900, regular month 1, day 1
  • The sum of Y includes all completed lunar years since 1900; the sum of M includes completed regular and leap months within the selected year
  • d is the lunar day, from 1 through the selected month length of 29 or 30 days

For lunar-to-Gregorian conversion, add the table-defined completed years, months and day offset to the epoch. Gregorian-to-lunar conversion reverses this process. Supported lunar years are 1900–2100, corresponding to Gregorian dates 1900-01-31 through 2101-01-28 inclusive. Regular and leap months with the same number are separate months.

What is a Lunar Calendar Calculator?

Definition:

This Lunar Calendar Calculator converts between Gregorian dates and the civil Chinese lunisolar calendar, including leap months. It also reports the lunar-year zodiac and stem-branch name, and finds the next matching month/day with the same leap status in a later supported lunar year. It does not calculate astronomical moon phases.

How to Use the Lunar Calendar Calculator?

Example Problem:

The following example converts a Gregorian date to the corresponding Chinese lunar year, month and day.

First, choose Gregorian to Chinese lunar and enter 2023-10-12.

The Hong Kong Observatory table maps Gregorian 2023-10-12 to Chinese lunar year 2023, regular month 8, day 28.

For the reverse conversion, choose Chinese lunar to Gregorian and enter year 2023, month 8, day 28, regular month. The result is 2023-10-12. A lunar date alone is not a calculated astronomical moon-phase time.

FAQ

What is the Lunar Calendar Calculator used for?

It converts Gregorian dates and Chinese civil lunisolar dates in either direction. Leap months, 29/30-day month lengths and the lunar year are accounted for explicitly. The next match preserves regular/leap status and starts with the following lunar year; it may skip years without that month or day.

Is the conversion based on accurate astronomical data?

The converter uses a fixed civil-calendar table consistent with the Hong Kong Observatory daily conversion tables over their 1901–2100 Gregorian coverage, with separately checked boundary extensions. It does not recompute new-moon or solar-term times. HKO warns that future events near midnight may cause a one-day difference in the assigned calendar date; consult an authoritative almanac for important observances.

When does the zodiac or stem-branch year change?

This calculator follows the civil convention in which the zodiac and stem-branch year change at Lunar New Year, the first day of the first lunar month. Some traditions use the Spring Commences solar term instead. No dummy moon-phase estimate is produced.