Date Difference Calculator
Free, no account, works offline.
Pick two dates and see the gap expressed every way it is usually needed: total days, weeks and days, calendar years and months, and working days.
What it does
- Total days, with an option to count both the first and last day.
- The same gap as years, months and days, and as weeks and days.
- Which weekday each date falls on.
- Add or subtract days, weeks, months, years or working days from any date.
The part most calculators get wrong
Whether both endpoints count. The 1st to the 5th is four days as a duration and five days as a count of days off — both are right, for different questions, and a calculator that silently picks one causes arguments. This asks.
Common questions
Should I include both the start and end date?
Include both when you are counting days that each have something happening on them — holiday allowance, notice periods, a conference. Leave it off when you are measuring elapsed time.
Why does adding one month to 31 January give 28 February?
Because there is no 31 February, and clamping to the last day of the target month is what calendars and contracts mean by a month. Overflowing into March would surprise everyone.
Does it handle dates far in the past?
It uses the proleptic Gregorian calendar, applying today's leap-year rule to every year. That matches what spreadsheets and databases do, but it is not how dates before 1582 were actually written.