Convert between solar (Gregorian) and lunar dates, find the zodiac animal for any year, and see a live countdown to the next Lunar New Year.
The lunar calendar tracks moon phases and inserts a leap month to stay aligned with the seasons. Months run 29 or 30 days, and with a leap month roughly every three years, the same lunar birthday can move more than 20 days against the Gregorian date.
It is not purely lunar. Months follow the moon (about 29.53 days), but leap months are inserted to keep the year aligned with the seasons.
Twelve lunar months total about 354 days, eleven short of the solar year. Left alone, the calendar would drift a month every three years and Lunar New Year would eventually fall in summer.
So seven leap months are added every nineteen years (the Metonic cycle). The result is that lunar dates oscillate within about ±15 days against the solar calendar without drifting.
This is unlike the Islamic calendar, which has no leap month and moves 11 days earlier every year indefinitely.
A month containing no major solar term (the even-numbered ones among the 24 terms) becomes a leap month.
A leap month takes the name of the month it follows — a leap fourth month is "another fourth month".
Korean tradition treats the leap month as an "empty month" when the gods are said to rest, which is why moving house, preparing burial clothes and relocating graves are customarily done then — believed to pass without misfortune.
Weddings, by contrast, were traditionally avoided during a leap month.
By Lunar New Year — the most common convention. The animal changes on the first day of the first lunar month.
By Lichun (start of spring) — used in Chinese astrology and Korean saju, changing around 4 February.
The two are usually days apart, so people born in late January or early February can be assigned different animals depending on which system is applied — which is why a fortune teller's answer can differ from the everyday one.
The animals combine with ten heavenly stems on a sixty-year cycle, which is why the sixtieth birthday returns to the stem-branch combination of one's birth year and is traditionally significant.
Solar terms are defined by the sun's position along the ecliptic, not by the moon. Their Gregorian dates are therefore nearly fixed — Lichun around 4 February, the summer solstice around 21 June.
The common assumption that solar terms are lunar is backwards. They exist precisely because a lunar calendar cannot tell you the season, and farming needed one that could.
That is why customs tied to solar terms — eating red bean porridge at the winter solstice, posting spring couplets at Lichun — recur on roughly the same Gregorian date each year.
Many families observe elders' birthdays and ancestral memorial rites by the lunar calendar. The Gregorian date shifts each year, so it is easy to miss without checking.
Birthdays falling in a leap month are particularly awkward, since a given leap month recurs only every few years. Convention observes them in the regular month of the same number.
Memorial rites are traditionally held on the eve of the anniversary, because the day was reckoned to begin at 11pm. Many families now hold them on the evening of the day itself.
Lunar calculation rests on astronomical computation — the moment of the new moon and the solar terms. In Korea the official calendar is published by the Korea Astronomy and Space Science Institute.
Korean and Chinese lunar dates differ by a day in some years, because the new moon's instant is evaluated against each country's standard time. A new moon near midnight lands on different dates.
Calculation happens in the browser and no dates are transmitted. For dates that matter, cross-check against an official source.
From the East Asian lunisolar calendar via the browser's built-in calendar data; regional observance can differ by about a day.
The animal changes at Lunar New Year, not January 1, so early-year dates belong to the previous year's animal.
Enter the lunar birthday and convert to solar — since the lunar calendar shifts against the solar calendar, the matching solar date changes every year.
What this tool bases its numbers on, and how far those numbers go.
Conversion is delegated to the runtime's Chinese lunisolar calendar (Intl with calendar «chinese»), which places new moons and the 24 solar terms astronomically. A lunar month runs 29 or 30 days; a month containing no major solar term becomes the leap month. The zodiac animal is taken from the lunar year, so it turns at Lunar New Year and not on 1 January.Why leap months exist: 12 lunar months are about 354 days, 11 short of a solar year. Adding 7 leap months every 19 years gives 19 × 12 + 7 = 235 lunar months ≈ 6,939.7 days, against 19 solar years ≈ 6,939.6 days — the two agree to within a day.