Count the days between two dates
Pick two dates above and you instantly see the difference in days, in weeks plus days, and as an exact years/months/days breakdown. By default the end date is not counted (June 1 → June 10 = 9 days); one checkbox includes it. Everything runs locally in your browser.
Counting nights vs. counting days
The default counts the distance between the dates — like nights in a hotel or the answer to "how many days until…". Including the end date counts both endpoints, which fits rental periods, medication courses or attendance: Monday through Friday is then 5 days instead of 4. Getting this distinction wrong is the most common off-by-one error in date maths.
How the breakdown works
The years/months/days breakdown anchors at the start date and counts full calendar months first, clamping month ends (January 31 + 1 month = February 28/29) — the same convention used for deadlines and ages. Because months differ in length (28–31 days), "3 months" is not a fixed number of days: across a year it averages about 30.44 days per month.
Typical uses
Project durations, notice periods, visa stays, pregnancy weeks, subscription periods, days until an event or between invoices — anywhere "how long is it exactly?" needs a precise, reproducible answer rather than a guess.
Private by default
Both dates are processed entirely on your device — no upload, no storage. The calculator works offline too.