Inclusive or exclusive — we show both
"How many days between 1 March and 10 March" has two defensible answers. Nine is the difference between the dates. Ten is the number of days you would cross off a calendar if you counted both ends. Neither is wrong; they answer different questions, and almost every argument about a date calculation is really this argument.
So this tool shows both numbers, labelled, at the same time. The exclusive count is the difference and is what you want for interest, notice periods and age. The inclusive count is what you want for hotel nights counted as days, jury service, and anything phrased as "from X to Y inclusive".
What else the answer shows
Alongside the day count you get the span expressed in weeks and days, in years, months and days, the number of working days after weekends and US federal holidays are removed, and flags for any leap day or daylight-saving change inside the span.
Worked example — a rental period
From 3 April 2027 to 28 September 2027 is 178 days exclusive, or 179 inclusive. That is 25 weeks and 3 days, or 5 months and 25 days. Removing fifty-one weekend days and the Memorial Day, Juneteenth, Independence Day and Labor Day observances leaves 123 working days. The span contains no leap day and one daylight-saving change (in November — outside this span, so none at all).
Worked example — a leap-year span
From 1 January 2028 to 1 January 2029 is 366 days, not 365, because 2028 is a leap year and the span contains 29 February 2028. Any calculation that assumes a year is 365 days will be one day out for spans crossing that date, which is a genuine source of quiet error in interest and accrual arithmetic. The tool flags it explicitly.
Dates before 1583
Dates are computed on the proleptic Gregorian calendar. For historical dates before the Gregorian reform, this will disagree with a contemporary Julian-calendar record by up to a fortnight. That is a limitation worth knowing about rather than a bug — see the methodology page.
The convention, stated plainly
The exclusive count is the difference between the two dates: subtract one from the other and that is the number. The inclusive count adds one, because it counts both endpoints as days. 1 January to 8 January is seven days exclusive and eight inclusive. Neither figure is the "real" one — the question decides. Interest, notice periods, age and any span you would describe as "X days later" want the exclusive count. Hotel nights, jury service, leave taken and anything worded "from X to Y inclusive" want the inclusive one. Because the wording almost never says which, this page shows both and labels them, rather than picking one and leaving you to discover the off-by-one later.
Worked example — a 100-day span that is not 100 days of anything else
From Tuesday 18 August 2026 to Friday 25 December 2026 is 129 days exclusive, 130 inclusive. That is 18 weeks and 3 days. Removing thirty-six weekend days and the Labor Day, Columbus Day, Veterans Day, Thanksgiving and Christmas Day observances leaves 88 working days — about two-thirds of the elapsed time. The span contains one daylight-saving change, on Sunday 1 November 2026, and no leap day. Every one of those figures is a different answer to "how long is it until Christmas", and which one you want depends entirely on whether the thing you are counting happens at weekends.
Leap days, and the 365-day assumption
From 1 January 2028 to 1 January 2029 is 366 days because 29 February 2028 sits inside it. From 1 January 2027 to 1 January 2028 is 365. Any calculation that treats a year as a fixed 365 days is therefore wrong for roughly one span in four, by exactly one day. That is small until it is a per-day interest calculation or a per-day rate on a long contract, at which point it is one day's money on every affected span. The tool flags a leap day inside the span explicitly rather than leaving you to notice. Leap years between 2020 and 2060 run 2020, 2024, 2028, 2032, 2036, 2040, 2044, 2048, 2052, 2056, 2060 — every four years without exception, because the next century year is 2100 and it is not a leap year. The full rule is on the leap year calculator.
Where other day counters disagree
- Inclusive by default. Some tools return only the inclusive figure and some only the exclusive, and very few say which. That single choice is the source of most arguments about date arithmetic.
- Timestamp subtraction. A tool that subtracts two timestamps and divides by 86,400,000 gets a fractional answer on a span crossing a daylight-saving change, and then rounds it — sometimes to the wrong integer. We work on calendar components, so a clock change cannot move the answer.
- Time-of-day contamination. Tools that attach a current time to each date will report 29 days between two dates 30 days apart if you happen to load the page in the afternoon. Dates here have no time component at all.
- Historical dates. We use the proleptic Gregorian calendar throughout, so a span reaching before 1582 will not match a contemporary Julian-calendar record.
Turning a day count into something more useful
A raw day count is rarely the end of the question. For the same span expressed in whole weeks plus a remainder, use weeks between dates. For the count with weekends and federal holidays removed and each holiday named, use working days between two dates. For a span measured from a birth date in completed years, months and days, use the age calculator — it applies the same start-date rule but reports in calendar units rather than raw days. To go the other way and find the date a given number of days away, use the date calculator.