Date Difference Calculator

How the date difference is calculated

Enter any two dates and the calculator breaks the gap down three ways: an exact span in years, months, and days; the total number of days and weeks; and the number of business days (Monday–Friday), with weekend days and custom excluded weekdays shown separately. If the dates are in the wrong order it swaps them automatically.

• Total days — the number of midnights between the two dates.
• Years / months / days — whole calendar years, then whole months, then leftover days, using real month lengths and leap years.
• Business days — every weekday in the range, minus any custom excluded weekdays you enter for holidays or closures.
• Include end date — adds the final day, turning an exclusive count into an inclusive one.

Worked example

From January 1, 2026 to December 31, 2026: 364 total days (52 weeks), which is 11 months and 30 days exactly. Of those, 260 are weekdays and 104 fall on weekends. Ticking "include end date" adds Thursday, December 31, making it a full 365 days with 261 weekdays — one calendar year.

Both days inclusive, or only one?

This is the question behind most "the answer is off by one" complaints. Elapsed time counts midnights, so January 1 to January 2 is one day. Counting both calendar dates makes the same range two.

When a document says "within 30 days of" a date, it usually means the day after that date is day one — the starting day itself is excluded. Courts and agencies often have their own written rule for this, and it beats any convention.

Business days and holidays

The weekday count removes Saturdays and Sundays, which suits invoice terms, shipping estimates, payroll periods, and project schedules. Public holidays are not universal — a federal holiday in one country is a working day elsewhere, and company closures vary — so the calculator does not guess them. Subtract the weekday holidays that fall in your range, or use custom excluded weekdays to drop a whole day of the week if your schedule also skips, say, every Friday.

US holidays that move every year, for the next three years:

Easter is the awkward one: as a lunisolar date it can land anywhere from March 22 to April 25. Christmas, New Year's Day, the Fourth of July, and Halloween are fixed and only change weekday.

Weeks and months between dates

Total weeks is total days divided by seven, so 45 days is about 6.43 weeks. Months are less uniform, because a calendar month has 28 to 31 days. The exact result counts whole years and months before leftover days; the approximate figure uses the average Gregorian month of 30.4375 days. Use the exact span for anniversaries and contract terms, and the decimal for rough comparisons — never divide by 30 and call it exact.

Leap years

The calculation uses real calendar dates, so February 29 counts in a leap year and short months are not treated as 30-day blocks. A year is a leap year if it divides by four, except century years, which must also divide by 400 — so 2024 and 2000 were leap years and 2100 will not be. It matters whenever a range crosses February or spans several years.

When the answer has legal or financial weight

Courts, contracts, employers, and agencies may use special rules for filing dates, holidays, weekends, time zones, and partial days. This is general calendar math, not a legally binding deadline; when a missed date has consequences, confirm it against the governing rule or a qualified professional.

Counting from a birth date? The age calculator adds a next-birthday countdown. For hours within a day or across midnight, use the time duration calculator.