Date Difference Calculator

Enter a start and end date to get the number of days, weeks and months between them, plus a precise years-months-days breakdown. Tick the box to count only business days (Monday–Friday).

Pick two dates and press Calculate difference.

How the difference is calculated

The whole number of days between two dates is the difference in their timestamps divided by the length of a day:

days = ( endDate − startDate ) ÷ 86,400,000 ms

Weeks are days ÷ 7, and the years-months-days breakdown borrows from larger units the same way age is calculated, using real calendar month lengths so leap years are counted correctly.

Worked example

From 1 January 2026 to 31 December 2026:

Days: 364 days between the two dates.
Weeks: 364 ÷ 7 = 52 weeks exactly.
Breakdown: 11 months, 30 days (2026 is not a leap year).

Counting business days

Business days exclude weekends — Saturdays and Sundays are skipped — which is how delivery windows, contract terms and payroll periods are usually counted. This calculator can switch to business-day mode, though public holidays are not subtracted automatically since they vary by country and state.

Note: the day count is exclusive of the start date and inclusive of the end (it counts the nights between). To count both endpoints as full days, add one to the total.

Frequently asked questions

How do I calculate the number of days between two dates?

Subtract the earlier date from the later one. The calculator converts both to timestamps and divides the difference by the milliseconds in a day to get whole days, then derives weeks and months.

Does it count leap years?

Yes. Because it works with real calendar dates, February 29ths are included in the day count and in the years-months-days breakdown.

What are business days?

Business days are weekdays, Monday through Friday, excluding Saturday and Sunday. They're used for shipping estimates and contract deadlines. This tool can count business days but doesn't subtract public holidays.

Is the start or end date included?

The day count is the number of nights between the dates — exclusive of the start and inclusive of the end. Add one if you need to count both endpoints as full days.

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Mustafa Bilgic · Editor, Calcool
Calculations use the Gregorian calendar and your device clock; nothing is uploaded. Public holidays vary by country and are not deducted in business-day mode. For age from a single birth date, see the Age Calculator.

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