Korean Lunar ↔ Solar Converter
Convert Korean lunar dates to solar and back — leap months, the sexagenary year, and the zodiac included.
How to use
- Pick a direction: solar → lunar, or lunar → solar.
- Enter the date. For a lunar date in a leap-month year, tick 윤달 (leap) if needed.
- Read the converted date, weekday, sexagenary year (간지) and zodiac animal.
Examples
This year’s date of a lunar birthday
If your birthday is lunar 8/15, switch to lunar → solar and enter the year you want: 2025 gives 6 October, 2024 gives 17 September. The gap between those two dates is why a lunar birthday cannot be stored as a fixed solar date — it moves by roughly eleven days each year, then jumps forward when a leap month is inserted.
A year with two sixth months
2025 has a leap 6th month. Lunar 6/1 without the 윤달 box converts to one solar date; the same 6/1 with the box ticked converts to a different one about a month later. Both are correct — they are different months that share a number, which is exactly the case a converter without leap-month support gets wrong.
Finding an ancestral rite date
Memorial rites (제사) are held on the lunar date of a death, so the solar date moves every year. Convert the lunar date once per year to know which evening it falls on. Families that hold the rite on the eve should convert the lunar date and then step back one day on the solar calendar rather than converting a date that is already shifted.
Planning around a lunar birthday
A lunar birthday can land as much as a month apart on the solar calendar between two consecutive years, because the lunar year is roughly eleven days shorter and a leap month occasionally pushes it back. Converting several years at once shows the pattern: early in most years, then a jump later in a leap-month year.
Born in a leap month
A leap month repeats the previous month, so a birthday in leap fourth month only recurs in years that also have a leap fourth month — which can be decades apart. In practice families pick a rule and keep it: either the same numbered day of the regular month, or the same day counted from the start of the leap month. The converter shows which years actually contain the leap month so you can see how rare it is.
FAQ
What date range is supported?
Lunar years 1900 through 2049, which covers solar dates from early 1900 to early 2050. Outside that range the tool refuses to answer rather than extrapolating: the Korean lunar calendar is not a formula you can extend, it is an astronomical table, so a date it does not have is a date it cannot convert.
What is a leap month (윤달), and how is it handled?
A lunar year of twelve months runs about 11 days short of a solar year, so roughly every second or third year an extra month is inserted to keep the calendar in step with the seasons. That extra month repeats the number of the month before it — a leap 6th month follows the regular 6th month — so in such a year two different dates are both “the 15th of the 6th month”. The 윤달 checkbox appears only for years that actually have a leap month, and only when the month you selected is the one that repeats. Asking for a leap month that a year does not have returns nothing rather than silently using the regular month.
Where does the data come from and how was it checked?
The conversion table follows the Korean lunar calendar dataset published by the Korea Astronomy and Space Science Institute (KASI), taken from an openly licensed reference implementation of it. Rather than trusting the table, every single day in the supported range was converted in both directions and compared against that reference — 55,134 solar-to-lunar conversions and the same number back — with no mismatches. Two sets of tests keep it that way. One pins the known anchors — Seollal and Chuseok for several years, the 2023 leap 2nd month, the 2025 leap 6th month, month lengths, the range boundaries. The other walks the entire range and checks that solar to lunar and back returns the original day, that every month is 29 or 30 days, and that each year’s months exactly span the gap to the next lunar new year.
Why does the zodiac animal not change on January 1?
The sexagenary year (간지) and its zodiac animal follow the lunar calendar, so they change at Seollal, not at the start of the solar year. Someone born in January or early February may therefore belong to the previous zodiac year. This tool reports the sexagenary year of the lunar date it computed, which is why a solar date in late January can still show the previous year’s animal.
How long is a lunar month?
29 or 30 days — never 31, and it varies month to month rather than following a pattern. That is why lunar day 30 exists in some months and not others: asking for the 30th of a 29-day month returns nothing instead of rolling over into the next month. The day selector only offers the days that month actually has.
Is the Korean lunar calendar the same as the Chinese one?
They use the same astronomical model but are anchored to different meridians — Korea to KST, China to CST. Month boundaries and leap-month placement depend on the exact moment of the new moon in local time, so a new moon just after midnight in one zone can fall before midnight in the other. Most dates agree, but occasionally the two calendars differ by a day and, rarely, place a leap month in different months.
Why are lunar months 29 or 30 days?
A lunar month is the interval between new moons, about 29.53 days. Since a calendar cannot use half days, months alternate between 29 and 30 days in a pattern determined by the actual new-moon times rather than a fixed rule. That is why there is no lunar 30th in some months, and why a lunar birthday on the 30th sometimes has no matching date.
Do Koreans celebrate lunar or solar new year?
Both, differently. Solar New Year on 1 January is a single public holiday. Seollal, the lunar new year, is a three-day holiday and is the larger family occasion, with rites, new-year bows and travel to hometowns. The zodiac animal changes at Seollal rather than on 1 January, which is why someone born in January can belong to the previous year animal.