CalcWhenDate Duration Calculator — Days Between Dates
From January 1, 2026 to December 31, 2026 there are 364 days between the two dates — 365 if you count both the first and the last day.
How it works
Pick any two dates and get the exact gap between them in days — the number you need for deadlines, rentals, notices, streaks and plans. The inclusive figure counts both endpoints, which is how most people mean it when they say a trip from Monday to Friday lasts five days.
Tick the business-days box to add a Monday-to-Friday count over the same span (holidays excluded — they differ by place). The order of the dates does not matter; the earlier one is always treated as the start.
The method
The duration is the difference of the two calendar dates in whole days, computed on UTC midnights so time zones and daylight saving cannot add or remove an hour. Inclusive duration adds 1. The business-day count walks the days strictly between start and end-exclusive convention used by date-difference tools, counting days whose weekday is Monday to Friday.
Frequently asked questions
Why is the answer one less than I expected?
Subtracting dates counts the boundaries crossed, not the dates touched. From Monday to Tuesday is 1 day, although two dates are involved. The inclusive figure on the results panel counts both dates, which matches everyday speech.
Does it count business days?
Yes — tick the box and a Monday-to-Friday count appears. Public holidays are not subtracted, because they vary by country and even by state.
What if the end date is before the start date?
The calculator simply swaps them and measures the span; the answer is the same either way.