Date difference calculator
Pick two dates to get the number of calendar days between them, plus weeks, months and the count of weekdays.
Business days skip weekends only; public holidays are not included.
How this calculator works
The number of days between two dates is an exact calendar difference: count every day from the start date forwards to the end date. That means the day after the start date is 1 day later, and including both endpoints adds one day. This distinction matters for deadlines, contracts and leave policies, which often specify inclusive counting.
Business days are different from calendar days because weekends are skipped. This calculator counts weekdays (Monday to Friday) between the dates but does not know about public holidays — if your project runs through a national holiday, subtract one day for each holiday that falls on a weekday. For financial and project purposes, business days are usually the relevant number, which is why the tool shows both. Months are approximate: dividing by the average month length (30.44 days) is fine for planning, but exact month arithmetic must be done on the calendar.
The formula
Calendar days = end date − start date (exclusive of the start day). Weeks = days ÷ 7. Months ≈ days ÷ 30.436875 (the average Gregorian month length, 365.2425 ÷ 12). Business days count each Monday–Friday encountered, excluding public holidays:
days = date(end) − date(start)
weeks = days / 7
months ≈ days / 30.436875
business days = count of Mon–Fri between the datesIf the end date is before the start date the difference is negative; business days are counted on the absolute interval.
Worked example
From Jan 1, 2026 to Oct 22, 2026 is 294 calendar days — 42.0 weeks or about 9.7 months. Of those days, 210 are weekdays, before subtracting public holidays.
Common mistakes
- Inclusive vs exclusive counting. A one-day meeting on a single date has 0 days difference. Add 1 if your policy counts both endpoints.
- Forgetting holidays. Business days here skip weekends only. Public holidays must be subtracted separately.
- Using months as exact. Month lengths vary from 28 to 31 days, so the month figure is only approximate.
Frequently asked questions
How do I count days between two dates?
Subtract the earlier date from the later one. For example, 1 January to 31 December is 364 days in a non-leap year.
Do business days include the start and end dates?
This calculator counts the weekdays strictly between the dates, excluding the start date. Business-day conventions vary by organisation, so check the policy you are applying.
How many working days are in a year?
A typical year has 260–262 weekdays. After 10–12 public holidays, most countries have about 250 working days.
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