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Korean Anniversary Calculator (100 Days)

Enter the day you started dating or a baby's birthday to see today's day count, plus dates for the 100th, 200th, 1000th days and 1st-3rd anniversaries.

Result

Pick a start date to see the result.

What you enter is processed only in this browser and is never sent to a server. How it works

A calendar marked with a heart and a gift box illustrate anniversary dates

How to use

  • Start date: the day you started dating, or the day a baby was born. This date is day 1.
  • Reference date: the date you want the day count for. It starts out as today. Change it to a date in the future and everything is counted from that date instead.

The large number at the top is the day count for the reference date. Right under it, one line gives the “Next milestone” with its name, date and D-day. The table below lists eight milestones in date order: Day 100, 200, 300, 500 and 1000, and the 1st–3rd anniversaries. Because the order is by date, the two kinds are mixed together. Day 300 is followed by the 1st anniversary, then Day 500.

The “D-day” column is the number of days from the reference date to that milestone. A milestone still ahead shows as D-27, the day itself as D-Day, and one already past as D+173. The next milestone’s row is in bold, and past rows are dimmed.

Why the start date is day 1

Couples in Korea celebrate the 100th, 200th and 1000th day together, and a baby’s 100th day has its own name, baegil. For all of these, the start date (the first day as a couple, or the day of birth) is day 1, not day 0. So day 100 comes 99 days after the start date, not 100, which is one day off from an ordinary “days since” count. In general, day N is the start date plus (N − 1) days.

Worked example

If you started dating on June 13, 2025, your milestones are:

Milestone Date Days since the start date
Day 100 September 20, 2025 99
Day 200 December 29, 2025 199
Day 300 April 8, 2026 299
1st anniversary June 13, 2026 365
Day 500 October 25, 2026 499
2nd anniversary June 13, 2027 730
Day 1000 March 8, 2028 999
3rd anniversary June 13, 2028 1,096

Set the reference date to September 28, 2026 and that date is day 473, with Day 500 as the next milestone (D-27). Day 300 is already behind you at D+173, and the 1st anniversary at D+107. Day 1000 lands between the 2nd and 3rd anniversaries, about 2 years and 9 months in.

The 1st anniversary is not day 365

A yearly anniversary is set by the calendar, the same month and day, and not by a number of days. With the start date as day 1, the 1st anniversary is day 366, or day 367 if a February 29 falls in between. In the example above, June 13, 2026 is 365 days after the start date, which makes it day 366. That’s why the table has no “Day 365” row, only the 1st–3rd anniversaries.

For the same reason, the number of days to the 3rd anniversary depends on the year you started. The example above passes February 29, 2028, so its 3rd anniversary comes 1,096 days after the start date. A couple who started on February 29, 2024 reaches theirs after 1,095 days.

Sources

Frequently asked questions

We count the day after we got together as day 1. How do I set that up?

Put the day after you got together in the start date field. Whatever date goes in that field is always day 1, so day 100, day 200 and the rest all move one day later. The yearly anniversaries move one day later too, so check those separately with the date you actually got together.

What happens if the reference date is before the start date?

The result says "It hasn't started yet." and gives no day count. The milestone table still appears, and its D-day column counts the days from the reference date to each milestone. With a start date of June 13, 2025 and a reference date of June 1, day 100 shows D-111.

What does the calculator show on day 100 itself?

The large number at the top reads day 100, and the Day 100 row in the table shows D-Day. The next milestone is picked with the current day included, so for that one day Day 100 is still listed as the next milestone. From the following day it moves on to Day 200.

We started on February 29. When are our anniversaries?

In years without a February 29, the anniversary is counted on February 28. If you started on February 29, 2024, the 1st anniversary is February 28, 2025, the 2nd is February 28, 2026 and the 3rd is February 28, 2027. The 100-day milestones are counted in days, so they aren't affected.

Does it still work after the 3rd anniversary?

The day count keeps going, but there are no new milestones. The table stops at Day 1000 and the 3rd anniversary. With a start date of June 13, 2025 and a reference date of June 14, 2028, you get day 1,098, the "Next milestone" line disappears, and every row in the table is dimmed as a past date (D+).

Can I use this tool for a baby’s 100th day and first birthday?

Enter a baby's date of birth as the start date, and Day 100 in the table is the baegil and the 1st anniversary is the dol. The Encyclopedia of Korean Culture describes baegil as the hundredth day counted from the day a child is born. It traces the custom to a time when medicine was undeveloped and many infants died in those first months, so a baby who had come through safely was celebrated. Dol is the baby's first birthday, one year after birth. Baegil is counted in days and dol by the calendar date, which are exactly the two ways this calculator counts.

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