Date Calculator
Count down to a date, find the days between two dates, or add days to a date.
Nothing here yet.
Enter a date and it is calculated right away.
How to use
- 01Choose the calculation at the top: D-day, date difference, or add and subtract.
- 02Choose or type the dates. For add and subtract, also enter a number and pick the unit (days, weeks, months).
- 03Check the result and, if needed, press [Copy summary].
If it does not work
Date looks wrong?
- If the start and end dates are swapped, they are swapped back automatically and a note appears.
- If the date picker does not open, type the date directly, like 2026-09-17.
FAQ
How is D-day counted?
It is the number of days from today to the target date. If the target is today it shows D-Day, and if it has passed it shows D+ with the days since. Today itself is not counted.
When should I turn on "Include start date"?
March 1 to March 3 is normally 2 days apart, but for nights of stay or working days where the first day counts, turn it on to get 3. It does not affect the month count.
What is January 31 plus one month?
February has no 31st, so the result is the last day of February (28 or 29). Month arithmetic always clamps to the last day of the month.
How do I find the 100th day?
In add and subtract, add 99 days to the base date to get the 100th day counting the first day as day 1. If the first day does not count, add 100 days.
About this tool
A tool that calculates the days left until a target date, the days, weeks and months between two dates, and the date a number of days, weeks or months before or after a base date. It shows the weekday too, and dates are calculated on this device only.
Updated