Date Difference Calculator

Find the exact time between two dates, including business days, or add and subtract days, weeks and months from a date. Free, instant, private.

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Total days
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Total weeks
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Business days (Mon–Fri)
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How to use the Date Difference Calculator

  1. In "Difference between dates" mode, pick a start and end date to see the full breakdown.
  2. Read the years, months and days, plus total days, total weeks and business days between them.
  3. Switch to "Add / subtract" mode to shift a date forward or backward.
  4. Choose add or subtract, enter an amount, and pick days, weeks, months or years; the result updates live.

Why use ZillaKit's Date Difference Calculator?

Counting the time between two dates by hand is surprisingly error-prone because months vary in length and leap years add an extra day. This calculator does the calendar arithmetic correctly, giving you the gap expressed two ways: as a natural years, months and days breakdown, and as precise totals in days and weeks. It also counts business days, meaning weekdays from Monday to Friday, which is exactly what you need for project timelines, notice periods, delivery estimates and working-day deadlines. A second mode lets you add or subtract a number of days, weeks, months or years from any date, so you can quickly answer questions like "what date is 90 days from now" or "what was the date six months ago". Everything updates instantly as you change the inputs and works the same on phone and desktop. All of it runs locally in your browser using JavaScript's native date handling, so leap years and month lengths are accounted for automatically, and nothing you enter is uploaded or stored.

FAQ

How are business days counted?

Business days are weekdays, Monday through Friday, between your two dates. The count excludes Saturdays and Sundays but does not account for public holidays, which vary by country and region.

Does the calculator handle leap years?

Yes. It uses native date arithmetic that automatically accounts for leap years and the differing lengths of each month, so the totals are exact.

What happens when I add months to a date near the end of a month?

Adding months keeps the same day number where possible. If the target month is shorter, the date rolls to that month's last valid day, following standard date behaviour.

Is my data uploaded anywhere?

No. All calculations run in your browser using JavaScript's Date object. Nothing you enter is sent to a server or stored.