Count the gap or count the dates
For a gap, imagine moving from the first date to the second. February 28, 2024 to March 1, 2024 takes 2 days, because February 29 is a leap day. If you are counting every date touched by an event, including its start and end, the same span covers 3 dates.
The same date entered twice gives zero days between dates, or one day with both dates included. An end date before the start returns the absolute gap and labels the direction.
Calendar days are not working days
The calculation uses the Gregorian calendar for years 1 through 9999. It includes Saturdays, Sundays, and holidays, and applies Gregorian leap-year rules throughout that range. Historical local calendar changes are outside its scope.
A deadline may follow a different counting rule. Check whether the organization counts the starting date and excludes holidays. To move forward or backward by a known number of days, use the date calculator.