Date Difference Calculator

Details

About this tool

Counts the time between two dates three ways at once, because the question genuinely has three answers: a total in days, a calendar span of years, months and days, and a count of working days.

Which one you want depends on why you are asking. A hotel booking, an interest period or a notice count wants days. An age, a length of service or a warranty period wants the calendar span. A delivery estimate, a contractual deadline or a project plan wants working days. Showing all three removes the need to convert between them and, more usefully, makes it obvious when the number you assumed was the answer is not.

The calendar span is not the day count divided by 30. Months are 28 to 31 days long, so the two disagree, and the disagreement grows with the span. It is computed by counting whole months forward from the start date - the way a person counts on a calendar - rather than by subtracting year, month and day fields, which is the shortcut that produces a negative number of days when the end day is earlier in the month than the start day.

The inclusive option decides whether the last day counts. Both conventions are used and neither is wrong: a hotel charges for nights, so check-in to check-out is exclusive, while a notice period or a holiday allowance usually counts both ends. Getting this backwards is an off-by-one on a date, which tends to be noticed by someone else.

Working days skip weekends and Polish public holidays, including the moveable ones. Everything is calendar arithmetic on day numbers with no time zone involved, and it runs in your browser.

Good to know

Questions people actually ask

Should the last day be counted?

It depends on the convention, and both are legitimate. A hotel charges by the night, so arrival to departure is exclusive. A notice period, a holiday allowance or a warranty usually counts both ends and is inclusive. The option is there because the tool cannot know which you mean, and being wrong here is an off-by-one on a date.

Why does the calendar span differ from days divided by 30?

Because months are not 30 days. February is 28 or 29, seven months are 31, and the difference compounds over a long span. The calendar span counts whole months forward from the start date, the way you would on a wall calendar, which is why it can read "2 years, 1 month and 3 days" where the division suggests something slightly different.

How are working days counted?

Monday to Friday, minus Polish public holidays, including the moveable ones - Easter Monday and Corpus Christi are computed rather than read from a fixed table, so future years stay correct. Holidays that fall at the weekend are not deducted twice.

Can I use a date before 1970?

Yes. The arithmetic is on calendar day numbers rather than Unix timestamps, so there is no epoch to run into and historical dates work normally.

Why does another calculator give a different answer?

Usually one of two reasons: it counts the last day and this one does not, or it derives the calendar span by subtracting date fields rather than counting months forward. The second produces visibly odd results - sometimes a negative number of days - when the end day of the month is earlier than the start day.