Chinese Lunar Calendar Converter

The Chinese calendar is lunisolar, which is a polite way of saying it refuses to choose. Each month begins on a new moon and runs 29 or 30 days, so the 15th of any lunar month is always a full moon; that is why the Mid-Autumn Festival, the 15th day of the 8th month, is always celebrated under one. But twelve moon-months add up to only about 354 days, eleven short of the solar year, and a calendar left to drift would soon put the "spring festival" in midwinter. The fix is elegant: every two or three years, one month is simply told to repeat itself.

That repeated month is the leap month, 闰月 (rùnyuè), and it is the gear that keeps the whole machine honest: seven leap months slot into every nineteen years, and the seasons stay put. Which month doubles is not a matter of taste. The calendar tracks the sun through twelve "major terms" spaced around the year; a lunar month that fails to contain one is declared the leap month, a rule determined by astronomy rather than committee. In 2023 it produced a second 2nd month; in 2025, a second 6th month. There is no leap month at all in most years, which is exactly why the date of Chinese New Year swings between January 21 and February 21 and back again.

One consequence surprises nearly everyone: because the lunar year changes hands at Chinese New Year rather than on January 1, a January or February birthday often belongs to the previous lunar year, and with it the previous zodiac animal. Someone born on February 1, 1983 arrived before that year's new year (February 13) and is a Dog of 1982, not a Pig of 1983, whatever the horoscope placemats say. Our converter works this out from the real calendar, and tells you when it matters.

In many Chinese families a person simply has two birthdays: the Western one on documents and cake, and the lunar one, 农历生日 (nónglì shēngrì), the one a grandmother remembers without being told. Because the two calendars slide against each other, your lunar birthday lands on a different Western date every year, wandering across a window about a month wide. Traditional milestones ride on the lunar side: the red-egg celebration at one month old, the sixtieth birthday that closes a full cycle of the calendar, the ancestral offering dates kept in the lunar count.

The sixty-year cycle is the part most Westerners never hear about. Years are not only numbered, they are named: each carries one of ten "heavenly stems" (which give it an element) paired with one of twelve "earthly branches" (which give it an animal), and the pairing repeats only after sixty years. 2026 is a Fire Horse year, the 43rd name in the cycle; the same name last appeared in 1966 and returns in 2086. When our converter hands you a year, it hands you the full identity, the same one a fortune-teller would start from.

There is no formula that maps one calendar onto the other; the lunar calendar is defined by the actual sky. Modern Chinese calendars are computed from the true positions of the sun and moon, a standard set by China's national calendar specification (GB/T 33661-2017) and maintained by the Purple Mountain Observatory, the institution that has issued the official almanac since 1929. Our converter uses an astronomical implementation of the same rules across 1900–2100, not a rounded lookup table, and we cross-check output against the Hong Kong Observatory's published conversion tables. When a date can't exist (a 30th day of a 29-day month, a leap month in a year that had none) we say so plainly instead of guessing.