b2KIT

Date Difference Calculator

Calculate the exact difference between two dates in years, months, weeks, days, and business days.

How to Use Date Difference Calculator

  1. 1

    Enter the first date

    Select or type the starting date for your calculation.

  2. 2

    Enter the second date

    Select or type the ending date to compare against.

  3. 3

    View the difference

    See the gap in years, months, days, weeks, and total days.

Tested tool guide Math and conversion tools Checked July 30, 2026

What Date Difference Calculator does, with a checked example

This calculator reports a calendar difference in years, months, and days as well as total days, complete weeks, remaining days, total months, and weekdays. It also adds or subtracts a selected number of calendar days from another date. Dates are created at local midnight so the visible day stays tied to the user-entered calendar value.

Worked example

A concrete input and expected output from the current implementation.

Input

Start 2026-07-01; end 2026-07-30

Expected output

29 total days; 4 weeks and 1 day

Elapsed-day difference excludes the starting instant. The separate business-day count includes weekdays encountered while walking across the selected endpoints.

How the result is produced

1

Calendar units are borrowed separately

Years, months, and days are calculated from calendar fields, borrowing days from the previous month when the end day is earlier than the start day.

2

Total days use elapsed milliseconds

The absolute time difference is divided by 86,400,000 milliseconds and rounded. Daylight-saving transitions can complicate local-midnight arithmetic in some timezones.

Good uses

  • Count days between project or travel dates.
  • Express a span as complete weeks plus remaining days.
  • Add a calendar-day offset to a known date.

Limits and checks

  • Confirm whether a policy counts the start date, end date, both, or neither.
  • Weekday totals do not remove public holidays.
  • Legal, payroll, and interest periods can use domain-specific conventions.

Common questions

Why can calendar months differ from total days?

Months have different lengths. One calendar month can span 28, 29, 30, or 31 days.

Are business days the same as working days?

Not always. This tool excludes Saturday and Sunday only. Local holidays, shutdowns, and alternate workweeks require a calendar specific to the organization.

References and verification

The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.

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