Find the days, weeks, months and years between two dates, or add and subtract days from a date.
Counts the days between the two dates - the start date itself is not counted, the end date is.
This tool covers the two things people most often need to work out by hand: the number of days, weeks, months and years between two calendar dates, and what date you land on after adding or subtracting a number of days, weeks, months or years from a starting date.
Use "date difference" when you have two dates and want to know how much time sits between them - counting down to an event, checking how long a project ran, or working out someone's exact age in days. Use "add or subtract days" when you have one date and a duration - for example, "an invoice is due 30 days from March 3" or "what date is 12 weeks before the deadline."
The years/months/days figure is calendar-aware, not just total days divided by 30 or 365. It counts whole calendar months between the two dates, then whatever is left over becomes days. This is why dividing the total day count by 30 will not always match the months shown - months have different lengths, so the calculator counts actual calendar months instead of a flat 30-day estimate.
Adding one month to January 31 lands on February 28 (or 29 in a leap year), since February has no 31st - the calculator clamps to the last valid day of the target month rather than rolling over into March. The same logic applies when adding years to February 29 in a non-leap year.
From January 15, 2020 to September 16, 2026 is exactly 6 years, 8 months, 1 day - or 2,436 total days (348 weeks and 0 days). Adding 45 days to September 16, 2026 lands on October 31, 2026, a Saturday.
Does this count the start date, the end date, or both?
The end date is counted and the start date is not - this matches how most contracts, deadlines and "days since" questions are meant to be read. A gap from Monday to Tuesday is 1 day, not 0 or 2.
How does this handle leap years?
Automatically. The total day count and the years/months/days breakdown both use real calendar dates, so a February 29 in the range is counted correctly without any extra input from you.
Why don't the months shown match total days divided by 30?
Because real months are not 30 days long. The calculator counts whole calendar months (which run 28 to 31 days depending on the month), then shows the leftover as days - so the breakdown will not line up with a flat 30-day estimate.
Can I add or subtract months or years, not just days?
Yes - switch the unit to weeks, months or years in "add or subtract days" mode. Months and years are added calendar-style (see the note above about month-end dates), not as a fixed number of days.
What happens if I add a month to the 31st of a month?
The result lands on the last valid day of the following month instead of rolling into the month after - adding one month to January 31 gives February 28 (or 29 in a leap year), not March 3.
Does the result show the day of the week?
Yes, in "add or subtract days" mode the resulting date includes its day of the week, which is useful for checking whether a deadline lands on a weekend.
Can I use this for contract terms or payment deadlines?
Yes - "add or subtract days" mode is built for exactly this: enter the start date, the term length, and the unit (days, weeks, months or years) to find the exact due date.
Can the end date be before the start date?
Yes - in "date difference" mode, put the earlier date in either box; the calculator always shows the gap between them as a positive duration.