How to use
- Countdown: pick the date you are waiting for — an exam, a trip, a wedding — and see how many days are left as D-n. Once the date has passed it switches to D+n.
- Anniversary: pick a start date, such as the day you met or a baby’s birthday, to see which day number today is, plus the dates of the 100th and 1,000th day and the first three anniversaries.
- Add an optional label and it is included when you copy the result, e.g. “Wedding D-45”.
How D-Day notation works
The n in D-n is simply the target date minus today, counted in calendar days. Time of day is ignored.
| Notation | Meaning | Example (target Jan 1, 2027) |
|---|---|---|
| D-88 | 88 days before the target | Oct 5, 2026 |
| D-1 | The day before | Dec 31, 2026 |
| D-Day | The target date itself | Jan 1, 2027 |
| D+1 | The day after | Jan 2, 2027 |
Day counts start at day 1
In anniversary mode the start date is day 1, the way couples and parents in Korea count a 100-day celebration. That means the 100th day falls 99 days after the start date.
| Start date | Day 100 | Day 200 | 1st anniversary | Day 1,000 |
|---|---|---|---|---|
| Jan 1, 2026 | Apr 10, 2026 | Jul 19, 2026 | Jan 1, 2027 (day 366) | Sep 26, 2028 |
| Jan 1, 2024 (leap year) | Apr 9, 2024 | Jul 18, 2024 | Jan 1, 2025 (day 367) | Sep 26, 2026 |
If you would rather count “100 days after” the start date, use the date add calculator instead — it returns the date exactly N days later.
Things to keep in mind
- “Today” comes from your device’s calendar, so if you are travelling the count follows local time.
- Only whole days are counted; this tool does not show hours remaining.
- Anniversaries land on the same month and day. A start date of February 29 is shown on February 28 in common years.
- For the full gap between two dates in years, months and days, try the date difference calculator.
FAQ
Is the target day D-0?
It is normally written “D-Day”. The day before is D-1 and the day after is D+1.
Why do the two modes differ by one day?
Countdown mode reports how many days have passed since a date, while anniversary mode counts the start date itself as day 1. For the same date, the anniversary number is always one higher.
How long is 1,000 days?
About two years and nine months. Starting on January 1, 2026, day 1,000 is September 26, 2028.