D-Day Countdown Calculator
Count the days until or since a date from your device's local today (D-N, D-Day, D+N). Updates automatically when the date changes.
Dates are calculated in your browser and are never stored or sent.
How the D-Day countdown works
How to use
- Enter the target date as YYYY-MM-DD or pick it from the calendar.
- The result appears as you type as D-N, D-Day or D+N, and you can copy it.
- Reset clears only the D-Day input; other date tools keep their inputs.
Calculation rules
- Today is your device's local date. While the page is open it is rechecked every 30 seconds and when you return to the tab.
- A future target shows D-N (days left), today shows D-Day, and a past date shows D+N (days elapsed).
- Calendar days between the dates are counted: if today is 2026-01-01 and the target is 2026-01-10, the result is D-9.
- Gregorian dates from 0001-01-01 to 9999-12-31 are supported; times of day and daylight saving are not used.
- Dates are calculated only in your browser and are never stored or sent.