How it works
The calculator counts calendar days from the start date to the end date. By default the start day is counted and the end day isn't, which is how most deadlines and durations work (Monday to Tuesday is 1 day). Tick "include the end date" to count both days, for things like hotel stays or event lengths.
Business days count Monday through Friday only. Public holidays aren't removed, since they differ by country and employer.
All math uses calendar dates rather than clock time, so daylight saving changes never add or lose a day.
Worked example
How many days from January 1, 2026 to December 31, 2026?
2026 isn't a leap year, so it has 365 days. Counting from Jan 1 up to Dec 31 gives 364 days (52 weeks). Including the end date gives 365 days.
From February 1, 2024 to March 1, 2024 is 29 days, because 2024 is a leap year.
Frequently asked questions
Does this include the start and end date?
It counts the start date but not the end date unless you tick the box. That matches how you'd say "3 days from Monday" is Thursday.
Are holidays excluded from business days?
No. Only weekends are excluded. Subtract any holidays that apply to you by hand.
How many days are in a year?
365, or 366 in a leap year. Leap years are divisible by 4, except century years that aren't divisible by 400 (2000 was a leap year, 2100 won't be).
Can the end date be before the start date?
Yes. You'll still get the number of days between them, with a note that the end date comes first.