What the results show
- Days between dates — the whole number of days from the start date to the end date, leap days included.
- Calendar span — the same gap expressed in years, months, and days the way you'd read it off a calendar.
- Total weeks — the full weeks in that span.
- Add or subtract — switch modes to shift a date forward or backward by a number of days and see the exact resulting date and weekday.
How it works
To measure a difference, the calculator counts the real days between your two dates, so months of different lengths and February 29ths are handled automatically — the order you enter them in doesn't matter. To add or subtract, it moves the start date by the number of days you choose and reports the day it lands on, rolling across month and year boundaries for you.
Frequently asked questions
Does the day count include both the start and end date?
The days-between figure is the number of full days from the start to the end date. If you need to count both endpoints (for example, billing days), add one to the result.
Does it handle leap years and different month lengths?
Yes. Both the day count and the calendar span use the actual calendar, so leap days and short or long months are counted correctly.
Can I subtract days to find a past date?
Yes. Switch to “Add or subtract days”, choose Subtract days, and enter how many days to go back. The exact date and weekday appear instantly.
Why do I see a dash instead of a result?
Every field needs a valid entry — two valid dates in difference mode, or a valid start date and a non-negative number of days in add/subtract mode. A dash shows until the inputs are complete.
Are my dates saved or uploaded?
No. The calculator runs entirely in your browser. Nothing you enter is stored or sent to a server.