Day Counter
Reference date
Counting method
One year is counted by date (the same day the following year), so it comes out the same under either method. If that day does not exist the next year โ February 29, for example โ we use the last day of that month.
How to count the days to or from a date
A day count is the number of days between your reference date and today. If the date is still ahead, the days remaining are written as D-14. The day itself is D-DAY. Once it has passed, you write D+14.
Counting anniversaries adds one more convention. In Korea, 100-day and 200-day marks are usually counted with the starting day as day 1. Under that rule, day 100 is the reference date plus 99 days. Count the day after as day 1 instead and day 100 is the reference date plus 100 days. The two are always exactly one day apart, so pick whichever one you mean in the calculator above.
A year is counted by date rather than by days. The same month and day in the following year is the one-year mark, which is why the result is the same under either method.
Frequently asked questions
Is the start date itself day 1?
It depends on what you are counting. In Korea, a 100-day mark or an anniversary is usually counted with the starting day as day 1. In D-day notation for an exam or a deadline, on the other hand, the date itself is 0 and the day before it is D-1. So the same date can give numbers a day apart depending on the method. This calculator lets you pick either one.
How do I calculate 100 days?
If the date itself is day 1, day 100 is the reference date plus 99 days. If the day after is day 1, it is the reference date plus 100 days. The two results are always exactly one day apart. 200, 300, 500 and 1,000 days follow the same rule.
What do D-day and D+1 mean?
D-day is the reference date itself. D-1 is the day before it, and D-14 is 14 days before. Once the date has passed you write it with a plus, as in D+1, meaning one day has gone by. Because this notation treats the reference date as 0, the number can be one off from the 'day N' count that makes the date itself day 1.
Can I save the date I calculated?
Not on this page. The calculation happens inside your browser, and the date you enter is neither saved nor sent to a server. If you want to keep a date, create an event in Kiyo and turn D-Day on. For a date that is still ahead, the days remaining appear at the top of your first screen every day.
โป Everything on this page is calculated inside your browser, and the date you enter is neither saved nor sent anywhere. How anniversaries are counted can differ by country and by situation, so treat the result as a reference.