Days between dates calculator
Count the days between two dates, or add days to one.
About this calculator
Use it for countdowns, notice periods, project deadlines and how long until a trip.
The count leaves out the start date, so today to tomorrow is 1 day. If your rules count both ends, add one. It counts calendar days, not working days.
How it works
Counts calendar days and leaves out the start date, so today to tomorrow is 1 day.
The story behind it
Where the idea came from: Joseph Scaliger, scholar, proposed a continuous count of days in 1583.
Calendars make counting days awkward: months vary in length, and the Gregorian calendar, introduced in 1582, skips some leap years. Scaliger's continuous count let astronomers avoid the problem altogether. Counting days in one unbroken line is the idea that makes a reliable date calculator like this one possible.
Why you can trust this calculator
- It runs in your browser. Nothing you type into it is sent anywhere.
- The method is explained on this page, so you can check it yourself.
- Free to use, with no sign-up.
- Results are estimates, so please double-check anything important.
- Spotted a mistake? Tell us and we'll look into it.
After 15 years as a mathematics educator, I built CalculStore to give students, teachers, professionals and anyone working with numbers simple, reliable tools.
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