D-day Calculator
Count days to or from any date, with automatic 100-day, 1000-day, and yearly anniversary milestones.
Anniversaries
How to Use
Choose the start date (e.g. anniversary, exam, birthday). Pick a future date to count down, or a past date to count up.
See the number of days elapsed (or remaining) instantly, also shown in weeks and months.
Common milestones (100, 200, 1000 days, plus yearly anniversaries) appear automatically. Add your own custom day count too.
FAQ
How is the D-day formatted?
Future dates show as D-N (e.g. D-100 = 100 days to go), past dates as D+N (e.g. D+50 = 50 days since), and the day itself as D-day.
How is the Korean "first day = day 1" counted?
In Korea, the 100-day couple anniversary often counts the first day as day 1. The tool shows both the standard (day 0) and Korean-style (day 1) counts so you can compare.
Which anniversaries are suggested?
100, 200, 300, 500, 1000, 2000, 3000 days, plus 1, 2, 3, 5, 10 years. You can also add a custom N-day.
Are leap years and time zones handled correctly?
Yes. The tool compares dates only — time zones don't matter, and leap years are computed exactly.
Is anything sent to a server?
No. All calculations happen in your browser; the date never leaves the page.
