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ToolBoxGenie

Date Difference Calculator

Calculators · Added 6 July 2026

Find the exact span between two dates, expressed as a calendar breakdown and as total days, weeks and months. A separate business-days count excludes Saturdays and Sundays, which is what most contracts and delivery estimates actually mean by 'days'.

Mode

How to use the date difference calculator

  1. 1Pick a start date and an end date.
  2. 2Read the calendar breakdown and the total counts below it.
  3. 3Check the business-days figure if you need working days rather than calendar days.
  4. 4Switch to Add/Subtract mode to shift a date forward or back by a number of days.

Examples

Project duration

Input
1 April 2026 to 8 August 2026
Result
4 months 7 days · 129 total days · 93 business days

Notice period

Input
Add 90 days to 8 August 2026
Result
6 November 2026

About the date difference calculator

Where date arithmetic goes wrong

Two conventions cause most disputes. The first is whether both endpoints count: a '30 day' notice period served on 1 June ends on 30 June under an inclusive count and 1 July under an exclusive one. The second is whether 'days' means calendar or working days — a 15-day turnaround is three weeks if weekends are excluded.

Contracts that specify neither are ambiguous by default, and courts generally read plain 'days' as calendar days. If a deadline matters, write 'calendar days' or 'business days' explicitly.

Months are not a fixed unit

Adding a month to 31 January is genuinely undefined — there is no 31 February. Different systems resolve it differently: some clamp to 28 February, others roll over to 3 March. The clamping convention is the more common and the less surprising, and it is what this tool uses.

When precision matters, specify durations in days. 'Within 90 days' has exactly one meaning; 'within three months' has at least two.

Frequently asked questions

Is the end date included in the count?
The day count is exclusive of the end date — from 1 January to 2 January is one day. If your contract counts both endpoints (an 'inclusive' count), add one to the figure shown.
How are business days counted?
Every Saturday and Sunday between the two dates is removed. Public holidays are not deducted, because they vary by country, state and industry — subtract your own holiday list from the result if you need a precise working-day figure.
Why is the month count not just days divided by thirty?
Months are between 28 and 31 days long, so the calculator steps through real calendar months rather than approximating. This is why 129 days shows as 4 months and 7 days rather than 4.3 months.

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