Date Difference Calculator

Example Calculation

From January 1, 2026 to December 31, 2026 is 364 days (365 if you also count the last day). That is 52 weeks and 0 days, and 260 business days on a Monday to Friday count, before holidays.

Use the "include the end date" box when you count both the first and last day, for example for a hotel stay or a lease term.

How It Works

Whether you are planning a project, counting down to an event or checking how long a lease runs, you often need the exact gap between two dates. This calculator takes a start date and an end date and reports the difference in several useful forms at once: total days, weeks and days, months and days, years-months-days, hours and business days.

Total days are calculated by finding the exact millisecond difference between the two dates and dividing by the length of a day, so leap years and varying month lengths are handled correctly. The months-and-days figure uses calendar arithmetic: it counts whole months between the dates and then the remaining days. The “include the end date” option adds one day to the count, which is common in hotel stays, leave requests and contract terms that count both the first and last day.

The business days result counts Monday through Friday only. It does not remove public holidays because holidays differ by employer, state and year. If you need a precise working-day figure, subtract the holidays that fall in your range from the result. For legal deadlines, always check how the governing rules count days — some exclude the first day, some include weekends, and some roll deadlines that fall on a weekend or holiday to the next business day.

If you enter the dates in reverse order the tool swaps them automatically, so you never get a negative number. For ranges spanning many years, the output remains accurate, but keep in mind that months are not a fixed length: 30 days is not always one month. When precision matters, rely on the days figure.

Formula Explained

Days = (end − start) ÷ 86,400,000 ms (+1 if the end date is included)

Weeks = ⌊days ÷ 7⌋ with remainder days. Business days = number of dates in range that fall on Monday–Friday.

Assumptions and limits

• Dates are compared as calendar days in the Gregorian calendar, including leap years, without times or time zones.
• Business days exclude weekends only. Public holidays are not excluded.
• Months are not a fixed length, so the months-and-days line is a calendar difference and not a fixed number of days.
• For a legal deadline, check how the governing rules count days, because some exclude the first day or weekends.