How to use
This calculator writes countdowns the way they are written in Korea and other parts of East Asia. D-60 means 60 days to go, D-Day is the day itself and D+1 is one day after it. Students write “D-100” on the board before an exam, and people count down to a wedding, a move or a due date the same way. It also lists milestones. In Korea, couples celebrate their 100th, 200th and 1,000th day together, and families celebrate a baby’s 100th day. The same counts work for 100 days without smoking, 1,000 days sober or 100 days of a new habit.
- Countdown: choose a target date and the result appears right away, such as D-44, D-Day or D+1. There is no Calculate button.
- Anniversaries: choose a start date to see the 100-day milestones and the 1st to 10th anniversaries in one list, in date order.
- Save to list: in Countdown, give the countdown a name and save it. It is still in the list below the next time you open this page.
- Share: turn the D-day you are looking at into a link you can send to someone else.
- Choose one of the two modes at the top.
- In Countdown, enter a target date and a name, such as “Final exam” or “Trip to Lisbon”. In Anniversaries, enter a start date and decide whether to turn on Count the start date as day 1. It starts on.
- If today is November 11, 2026 and the target date is December 25, 2026, the result shows a large “D-44”, with the target date “December 25, 2026 (Fri)” below it. In Anniversaries, a start date of January 1, 2026 gives a list that begins with “100 days: April 10, 2026 (Fri)”.
Use it to count the days left until an exam or a certification test, a trip, a move or a baby’s due date. Use it also to find the 100th or 1,000th day since you met someone, got married, had a baby, quit smoking or started training.
When you read the result, look at the sign after the D. D- is the number of days left until the date, and D+ is the number of days since it. On the target date itself, the result is “D-Day” with no number. In the anniversary list, the nearest milestone that is today or later is marked Next, and milestones that have passed are shown dimmed.
How it works
- D-Day is the target date itself. The day before it is D-1 and the day after it is D+1.
- The n in D-n is the target date minus today, in days. Today is not counted. It is the same number you get in the Date Calculator’s Between two dates with today and the target date and Count the start date as day 1 off.
- Today is the date on your device. If you leave the page open past midnight, the count updates to the new date when you come back from another tab or app, or click the window again.
- 100-day milestones: with Count the start date as day 1 on, a milestone is the start date plus one day less than its number, such as 99 days or 199 days. With it off, the full number of days is added, so every milestone is one day later.
- Anniversaries are the same calendar date each year, whether the switch is on or off. If you started on February 29, the anniversary is February 28 in years without a February 29.
- The list covers 10 years from the start date: 36 day milestones from 100 days to 3,600 days, and 10 anniversaries. When a day milestone and an anniversary fall on the same date, the day milestone is listed first.
- Leap years are followed. You can enter dates from 1900 to 2100.
Why the start date counts as day 1 by default
Most deadline rules do not count the first day: the count starts the next day. The D-n count and Count the start date as day 1 switched off both work that way. Milestones like a 100th day together or a baby’s 100th day are a custom rather than a rule, and they are usually counted with the first day as day 1, so the switch starts on.
What saved countdowns and share links contain
- You can save up to 20 countdowns, with names of up to 20 characters. A countdown saved without a name is listed as “No name”.
- The list shows today’s and upcoming countdowns first, nearest first, followed by past countdowns, most recent first.
- Tap a row to load its target date and name and switch to Countdown. Tap the trash icon to delete the row at once. You then have 5 seconds to press Undo.
- A share link holds only the fields shown in the current mode: the target date and name in Countdown, or the start date and the switch in Anniversaries. Your saved list is never put in the link.
Examples
Every result below was produced by this calculator. The dates are made up.
Countdown (today is November 11, 2026)
| Target date | Result |
|---|---|
| November 12, 2026 | D-1 |
| November 26, 2026 | D-15 |
| December 25, 2026 | D-44 |
| January 1, 2027 | D-51 |
| March 15, 2027 | D-124 |
| November 11, 2026 | D-Day |
| November 10, 2026 | D+1 |
| January 1, 2026 | D+314 |
If you fly out on January 1, 2027, today is D-51. That trip’s D-100 was September 23, 2026. To find the date that is D-100 for any event, open the Date Calculator and subtract 100 days from the target date.
Anniversaries (start date January 1, 2026)
| Milestone | Start date counted as day 1 (on) | Start date not counted (off) |
|---|---|---|
| 100 days | April 10, 2026 (Fri) | April 11, 2026 (Sat) |
| 200 days | July 19, 2026 (Sun) | July 20, 2026 (Mon) |
| 300 days | October 27, 2026 (Tue) | October 28, 2026 (Wed) |
| 1st anniversary | January 1, 2027 (Fri) | January 1, 2027 (Fri) |
| 500 days | May 15, 2027 (Sat) | May 16, 2027 (Sun) |
| 1,000 days | September 26, 2028 (Tue) | September 27, 2028 (Wed) |
The day milestones move by one day with the switch, but the 1st anniversary stays put. If you started dating on January 1, 2026 and count that day as day 1, your 300th day is Tuesday, October 27, 2026.
A new start (start date November 11, 2026, switch on)
| Milestone | Date |
|---|---|
| 100 days | February 18, 2027 (Thu) |
| 1st anniversary | November 11, 2027 (Thu) |
| 1,000 days | August 6, 2029 (Mon) |
Whether it is a baby born today or the first day without a cigarette, the day itself usually counts as day 1, so leave the switch on. If you add 100 days to November 11, 2026 in the Date Calculator, you get February 19, 2027. That count starts the day after, so it is one day later.
Starting on February 29 (start date February 29, 2024, switch on)
| Milestone | Date |
|---|---|
| 1st anniversary | February 28, 2025 (Fri) |
| 4th anniversary | February 29, 2028 (Tue) |
| 1,000 days | November 24, 2026 (Tue) |
Edge cases
- D+n and “day n” are one day apart. If January 1, 2026 is day 1, April 10 is day 100. But if you enter January 1 in Countdown and look on April 10, you see D+99. D+ counts days since the date, so the start date is not included. To know which day you are on, add 1 to the D+ number, or use Anniversaries.
- Counting the start date or not moves every day milestone by one day. If you celebrate with someone, agree on how to count first.
- On the target date no days are left, so the result is D-Day, not D-0.
- Someone abroad may see a different number. Today is the date on each person’s device, so two people in different time zones can be one day apart around midnight.
- Saved countdowns live in this browser only. Clearing your browsing data or closing a private window can remove them. If your browser blocks storage, the saved list does not appear at all.
- Milestones beyond 10 years are not listed. For 5,000 days or a 20th anniversary, open the Date Calculator and add the days or years to the start date. If the start date counts as day 1, add one day less, such as 4,999 days.
Frequently asked questions
Does the D-day count include today?
No. Today is not counted in the days left. If the target date is tomorrow, the result is D-1. The result also says “Today is not counted in the D-day number”.
Is the 100th day counted from the day we met?
It usually is, so Count the start date as day 1 starts on. If you met on January 1, 2026, your 100th day is April 10. If you count the day after you met as day 1, turn the switch off and the 100th day is April 11.
Why can’t I see my saved countdowns on another device?
Saved countdowns are kept in this browser and are not sent to a server, so other devices and other browsers do not have them. To move one, create a share link, open it on the other device, and save it there.
Can the person I share a link with see my list?
No. The link holds only what is on the screen: the target date and name, or the start date and the switch. Your saved list is not sent.
It’s past midnight and the number hasn’t changed.
If the page stays open past midnight, it counts again when you return from another tab or click the window. If the number still has not changed, reload the page, and check the date and time zone settings on your device.
Can it count business days or skip holidays?
No. Every calendar day counts, including weekends and public holidays.
How it works
The count is the target date minus today, in days. Today is the date on your device, and today itself is not counted. When 0 days are left the result is D-Day, when days are left it is D-n, and when the date has passed it is D+n. A 100-day milestone is the start date plus n − 1 days when Count the start date as day 1 is on (the default), or plus n days when it is off. The 1st to 10th anniversaries fall on the same date each year, and February 29 moves to February 28 in common years. Saved countdowns stay in this browser only.
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