Gregorian → Chinese Lunar Date Converter

The Chinese "lunar" calendar is not purely lunar — it is a lunisolar calendar. Months follow the Moon, while the year stays anchored to the Sun. Each lunar month begins at the new moon (the instant the Sun and Moon share the same ecliptic longitude), which is day one; the full moon falls around the fifteenth. A synodic month averages about 29.53 days, so lunar months alternate irregularly between 30-day "long" months and 29-day "short" months — and which is which must be computed astronomically each year, with no fixed rule.

Here is the problem: twelve synodic months add up to only about 354 days, roughly 11 days short of the tropical year (~365.24 days). Left uncorrected, Lunar New Year would drift earlier every year and land in summer within a couple of decades. To keep months aligned with the seasons, the calendar inserts a leap month every two to three years — about seven times in nineteen years. That is what makes it lunisolar: the Moon's phases define the months, while the Sun's position frames the year.

The calendar remains woven into daily life across the Chinese-speaking world: Lunar New Year (the first day of the first month), the Dragon Boat Festival (fifth day of the fifth month) and the Mid-Autumn Festival (fifteenth day of the eighth month) all follow it, and many families still record elders' birthdays and ancestral memorial days in lunar dates. Converting between the two calendars remains an everyday need.

There is no simple formula linking the Gregorian and Chinese lunar calendars. The Gregorian calendar is purely solar with fixed month lengths; the lunar calendar's months are set by actual new moons and its leap months by the distribution of solar terms — both requiring precise astronomical computation. This is why people traditionally consulted a 萬年曆 ("ten-thousand-year almanac"): a pre-computed lookup table produced by astronomers.

This tool does not use a lookup table. It computes the conversion astronomically at request time: first locating the new moons around the target date to determine which lunar month the date falls in and which day of that month it is, then using the solar-term distribution to number the month and decide whether it is a leap month. Day boundaries follow UTC+8 — the standard reference meridian used by the official calendar.

Alongside the lunar date, the converter also reports the GanZhi (sexagenary) three pillars and the zodiac animal, and flags exact transition times on solar-term days — details that matter especially for BaZi chart work, explained in the sections below.

The intercalation rule is called "no zhōngqì, leap month" (無中氣置閏). The 24 solar terms split into 12 節 (jié, section terms) and 12 中氣 (zhōngqì, mid-point terms); normally every lunar month contains one zhōngqì — for example, the month containing the winter solstice is always month eleven. But because a synodic month is slightly shorter than the average gap between two zhōngqì, occasionally a whole lunar month contains no zhōngqì at all. That month is designated the leap month and reuses the previous month's name — for example the leap sixth month of 2025.

People born in a leap month face a practical puzzle — most years have no leap month, so when is the birthday? A common convention is to celebrate on the same day of the regular month in ordinary years (born on leap-sixth-month day 5 → celebrate sixth-month day 5), and some families simply switch to the Gregorian birthday. This converter clearly marks leap months with 閏 so you never confuse a leap sixth month with the regular sixth month.

GanZhi combines the ten heavenly stems (甲乙丙丁戊己庚辛壬癸) with the twelve earthly branches (子丑寅卯辰巳午未申酉戌亥) into a 60-unit cycle — the famous "sixty jiǎzǐ". Every year, month and day carries its own GanZhi pair. The three pillars this tool reports — year, month and day — are the first three pillars of a BaZi (Four Pillars) chart.

Note that the year boundary has two schools. In folk custom, the zodiac animal changes at Lunar New Year (the first day of the first lunar month) — the everyday "new year, new animal" convention. But BaZi practice starts the year at 立春 (Start of Spring), which usually falls between February 3 and 5 and can land either before or after Lunar New Year. For dates between 立春 and Lunar New Year the two schools disagree, so this tool shows both results with their basis labelled: use the 立春 school for BaZi, the Lunar-New-Year school for folk reckoning.

The month pillar's boundary is not the lunar month either — it is the monthly 節 term: each BaZi month begins at the exact transition moment (the 寅 month at 立春, the 卯 month at 驚蟄, and so on). This tool reports the month pillar at day granularity — a term day displays the new month's pillar for the whole day — and flags the exact transition time on term days as a reminder: for births on a transition day, the precise moment decides which month pillar applies.

No hour pillar is provided, because it requires a birth time. For a complete four-pillar BaZi chart with the Ten Gods, use our free BaZi chart tool, which handles the hour pillar and explains true-solar-time considerations.

Looking up lunar birthdays: elders' birthdays and ancestral memorial days are often recorded in lunar dates — enter the Gregorian date to cross-reference. The GanZhi and zodiac fields also settle the classic question of which animal someone born in January or February really is: those weeks may still belong to the previous lunar year, which is why the zodiac is so often miscounted for them.

Festival cross-referencing: to find which Gregorian date a lunar festival falls on in a given year, estimate a Gregorian date, convert, and adjust by a few days. Chart work: BaZi and ZiWei DouShu charts are built on the lunar calendar and GanZhi, so this converter works as a quick pre-chart check — or use our free ZiWei and BaZi chart tools, which do all conversions automatically.

New-moon and solar-term instants are computed astronomically at request time — not approximated from lookup tables. The supported range is Gregorian 1900 to 2100, with day boundaries at UTC+8. We do not store your query or use it for any other purpose: the conversion runs on the server and returns directly.

Honest note: different almanacs can disagree by one day in edge cases — a new moon falling close to midnight, or historical calendar-reform periods — due to algorithmic precision and time-zone baselines, not because either side is "wrong". Our computation methods and engine details are public on our methodology page: /methodology. If you find a result that differs from an authoritative almanac, we welcome a report so we can verify it.