Date difference calculator

How to use it

1. Choose a start date and an end date.
2. Tick Include the end day if you are counting something like a hotel stay or a trial that includes the last day.
3. Read the results: total days, weeks and days, calendar years and months, business days and weekend days.

Inclusive or exclusive counting?

This is the single most common source of confusion. From March 1 to March 8 is 7 days if you count the gap between the dates, or 8 days if both the first and last day count. Contracts, notice periods and hotel bookings often use different conventions, so check what your document means before relying on a number. The checkbox lets you switch between the two and see the difference immediately.

Worked example

From January 1, 2026 to December 25, 2026 there are 358 days, which is 51 weeks and 1 day. In calendar terms that is 11 months and 24 days. Of those days, 256 fall on weekdays and 102 fall on weekends. Tick the include option and the total becomes 359 days.

Business days

The business day figure counts Monday through Friday only. It does not remove public holidays, because holidays differ by country, state and employer. If you need working days for a US contract, start with the business day number and subtract the federal holidays that fall inside your range. There are eleven federal holidays, and several of them move each year because they fall on a particular weekday rather than a fixed date.

Leap years

A year is a leap year if it is divisible by 4, except for years divisible by 100 that are not divisible by 400. That is why 2000 was a leap year and 1900 was not. The next leap day is February 29, 2028. The calculator uses full calendar arithmetic, so leap days inside your range are counted automatically.

Why "months" is a fuzzy unit

Days and weeks are fixed. Months are not: they run from 28 to 31 days, so the number of months between two dates depends on the calendar, not on a simple division. The calculator reports complete calendar months, counting from the start date to the same day number in a later month. For anything financial, such as interest or rent, check whether your agreement uses actual days or a 30-day month convention, because the totals differ.

Common uses

• Project planning: business days until a deadline.
• Contracts and notice periods: 30, 60 or 90-day windows, where the inclusive question matters.
• Travel: nights versus days, since a hotel charges for nights.
• Personal milestones: days until a wedding, a due date or a move.
• Invoicing: days a payment is past due, which often decides late fees.

Time zones and daylight saving

This tool works with whole calendar days and ignores clock time, so daylight saving transitions do not change the count. If you need an exact number of hours across a daylight saving change, remember that one day in March has 23 hours and one day in November has 25 hours in most of the United States. Arizona and Hawaii do not observe daylight saving.

Dates before 1970 and far in the future

The calculator handles dates well outside the usual computer range, so birth dates from the 1930s or planning dates in 2090 work fine. Keep in mind that the Gregorian calendar was adopted at different times in different countries, so historical dates before the 1750s in English-speaking countries can be ambiguous in old records.

Last reviewed on September 15, 2026 by the Dailycaltor team.