Days Between Dates Calculator
Calendar days are counted from the start date to the end date. Business days skip Saturdays and Sundays.
Pick the two dates to compare
Enter the start date and end date. Choose whether you want a simple elapsed day count or an inclusive count that includes both dates.
Use elapsed days for age style duration and most date subtraction. Use inclusive days when a form, booking period or instruction says both the first and last date count.
If the answer will be used in a policy or contract, write down which counting rule you used. That prevents later confusion.
Calendar days versus business days
Elapsed days counts how many midnights are crossed from the start date to the end date. If the dates are Monday and Tuesday, the elapsed difference is 1 day.
Inclusive days counts the dates themselves. Monday through Tuesday inclusive is 2 calendar dates. This is not a contradiction. It is a different counting rule.
How the day count is made
For elapsed days, the calculator subtracts the start date from the end date using calendar date values. Leap years are naturally included because the calendar has an extra February 29 when needed.
For inclusive days, it adds 1 to the elapsed count when the end date is on or after the start date. That extra 1 represents the starting date as a counted day.
Counting days until an event
From June 1 to June 10, the elapsed difference is 9 days. That is because nine day steps take you from June 1 to June 10.
If the instruction says June 1 through June 10 inclusive, the answer is 10 dates. Both June 1 and June 10 are included in the count.
Neither answer is more correct by itself. The correct answer depends on whether you are measuring elapsed time or counting calendar dates.
Inclusive date counting
The most common mistake is not deciding whether the count is inclusive. Many real questions are ambiguous until you know whether the first day, last day or both are counted.
Another mistake is including time of day by accident. If one value has a hidden time, a spreadsheet may return a result that seems off by a fraction or one day.
Days Between Dates Calculator FAQ
What does inclusive mean when counting days?
Inclusive means the endpoint dates count as part of the range. If a range says March 1 to March 5 inclusive, it includes March 1, March 2, March 3, March 4 and March 5.
That gives 5 dates, even though the elapsed difference from March 1 to March 5 is 4 days.
Should I include the start date when counting days between dates?
It depends on the context. For elapsed time, do not include it as a full extra day. For attendance, booking, leave or date range wording, you may need inclusive counting.
If the instruction says through, inclusive or including both dates, inclusive counting is usually intended.
Why is the difference from today to tomorrow one day?
Because one day step passes between the two dates. The calculator is measuring elapsed time, not counting date labels.
If you count both today and tomorrow as dates on a calendar, you get two dates. That is a range count, not an elapsed difference.
Do leap years affect days between dates?
Yes, when the range crosses February 29 in a leap year. The calendar has an extra day, so the elapsed count includes it.
You do not need to add it manually. A calendar based calculator should include February 29 when it exists in the range.
Why does my spreadsheet show a date instead of a number of days?
The cell may be formatted as a date. Date subtraction can produce the correct numeric difference, but the spreadsheet may display that number as a calendar date.
Change the result cell to number format before assuming the formula is wrong.
This happens because spreadsheets store dates as serial numbers. The math may be right even when the display format is misleading.