Exclusive Date Difference
Days between two dates, not counting the end
The subtraction answer — the distance from one date to another, which is what a deadline, an age and every date library mean by a difference.
Questions people ask
The things that come up about exclusive date differences, answered plainly.
Why is this the default everywhere in software?
Because it composes. Exclusive differences add up: the gap from A to B plus the gap from B to C equals the gap from A to C. Inclusive counts do not, which is why every date library subtracts.
Related tools
How far apart two instants are — in whichever unit you need, counting every day or only the working ones.
Inclusive Date DifferenceThe count that includes the first day and the last — what a hotel bill, a jury summons, a sick note or a "within 30 days" clause almost always means.
Days Between DatesA plain day count, with the weekday split beside it and the inclusive answer stated too — because half the time "days between" means one more than subtraction gives.
Date Difference CalculatorEnter two dates and get the gap in every unit at once — years, months and days as a person would say it, and the exact total in weeks, hours, minutes and seconds underneath.
Duration CalculatorA duration in every unit from nanoseconds to decades, with the approximate ones flagged as approximate — because a month has no fixed length and any tool that pretends otherwise is guessing.