About this tool
This D-Day calculator counts the number of days between today and a date you choose. A future date shows as D-n, today is D-Day, and a past date shows as D+n. The anniversary mode takes a start date, such as the day you started dating, and lists the dates of milestones like day 100, 200, 300, 500, 1000 and each yearly anniversary. In Korean style the start date itself is day 1, so day 100 falls 99 days after the start. For example, if you start on 2026-01-01, day 100 is 2026-04-10 when counted the Korean way, or 2026-04-11 if you count the start as day 0. The first anniversary is the same calendar date one year later. Dates use your device's current date and calendar days only, so time of day and time zones are ignored. Everything is calculated in your browser and nothing is sent to a server. Check the counting rule of any contract or exam before relying on a result.
How to use
- Open the 'D-Day countdown' tab and pick a target date to see D-n or D+n.
- Or open 'Anniversaries' and pick your start date.
- Turn the Korean-style option on to count the start date as day 1.
- Share the page with your partner or friends.