Why lunar dates move
Twelve lunar months add up to about 354 days, roughly eleven days short of a solar year. Lunisolar calendars catch up by inserting a leap month every few years. So the same lunar date arrives about eleven days earlier each year, then jumps later after a leap month.
How far they move
Holidays in the Korean calendar:
| Lunar date | 2026 | 2027 |
|---|---|---|
| 1st month, day 1 (Lunar New Year) | Feb 17 | Feb 7 |
| 4th month, day 8 (Buddha’s Birthday) | May 24 | May 13 |
| 8th month, day 15 (Chuseok) | Sep 25 | Sep 15 |
Calendars computed for different time zones can occasionally put the same lunar date on different solar days, so use the calendar your family follows.
Converting to solar dates
- Open a lunar-to-solar converter, such as the one from the Korea Astronomy and Space Science Institute.
- Enter the year and the lunar month and day; mark it if the birthday is in a leap month.
- Look up this year and the next two or three at once.
For birthdays in a leap month, families decide differently which day to celebrate in years without that leap month. Agree on it in advance.
One entry per year
Add each year without repeat
In D-Day Counter, add “Dad’s birthday 2026”, “Dad’s birthday 2027” and so on, each with Repeat set to None. Yearly repeat follows the solar calendar and will drift.
Note the lunar date in Memo
Write the lunar month and day in Memo so next year’s lookup is quick. Use the Birthday category so they group together in Stats.
Tidy up past years
Non-repeating items stay as D+ after they pass. Delete old ones or sort by Nearest.
The app’s English screenshots below still show sample titles in Korean (an exam and a wedding anniversary).
FAQ
Should we celebrate the solar or the lunar birthday?
Families differ. If you keep both, use Yearly repeat for the solar one and per-year entries for the lunar one.
Is legal age based on the lunar birthday?
No. In Korea, legal age follows the registered date of birth. See Korean age vs international age.
Sources: Korea Astronomy and Space Science Institute, lunar-solar converter · Shiftee, 2026 Korean public holidays (Korean) · Financial News, 2027 calendar announcement (Korean)
D-Day Counter · Days Until / Since
No sign-up: just a title and a date. Everything stays on your phone. Free on Android, in English and Korean.