Lunar to Gregorian Date Calculator

The Chinese lunisolar calendar names months and days within a lunar year that starts on Lunar New Year. Converting to the Gregorian calendar requires knowing which years have leap months and how many days each lunar month contains — full conversion needs a complete almanac.

This tool approximates by counting days forward from the Lunar New Year lookup for your year, using an average month length. It is useful for rough “when is lunar month 8 day 15?” style questions but can be off by days or more when leap months apply.

Example: lunar year 2026, month 1, day 1 should align with Lunar New Year 2026 (February 17, 2026). Mid-year lunar dates drift from precise tables — confirm important events with an official calendar.

A lunar month is a real astronomical period, not a rounded one. The synodic month averages about 29.53 days, so months alternate irregularly between 29 days (called short months) and 30 days (long months) in a pattern set by observed new moons rather than by a repeating rule. That is why no simple arithmetic reproduces the calendar exactly.

Leap months are the largest source of error in any approximation. Roughly every second or third year the calendar inserts an extra month, which repeats the previous month's number with a leap marker (閏), and a lunar year can therefore run 383 to 385 days. In a leap year, a date late in the year can be off by a full month if the intercalation is ignored.

Which month gets doubled is determined by the solar terms. The traditional rule inserts a leap month where a month contains no principal solar term, so the position varies year to year — it is not fixed like February 29 in the Gregorian calendar.

This matters most for the dates people actually look up. Mid-Autumn Festival on month 8 day 15, Dragon Boat Festival on month 5 day 5, and Qingming all shift relative to a simple day count, so cross-check anything you are booking travel or a ceremony around against a printed almanac or an official calendar.

Historical dates need more care still. Calendar reforms, changes in the reference meridian, and the switch from observed to calculated new moons mean that pre-twentieth-century conversions can differ between sources — treat older results as approximate unless you are using a specialised historical almanac.

Historical calendar reforms mean very old dates may not match modern conversion tables — treat pre-20th-century results as approximate unless you use a specialized almanac.

Double-check whether your source date used civil midnight or astronomical new moon — festival tables occasionally differ by one Gregorian day.