How working days are counted — and why 'within 5 business days' means different things

"Delivery within 5 working days" ordered on a Friday afternoon before a bank-holiday Monday could mean the following Friday or the Monday after, depending on who is counting. Working-day arithmetic is simple and the conventions aren't shared, which is why the working days calculator makes its assumptions explicit. This guide lays them out so you can too.

The counting conventions

Three questions decide the answer. Does day zero count? Most conventions say no: "5 working days from Monday" is the following Monday, counting Tuesday as day one. Is there a cut-off time? Orders after 2 p.m. often count from the next day. And is the end day inclusive — "by" the fifth day, meaning close of business on it? Contracts usually say; shops usually don't. The safe reading, for planning, is the latest one: exclusive of the start day, after any cut-off, to the end of the final day.

Weekends and public holidays

Working days exclude Saturdays and Sundays in most of the world (Friday and Saturday in some Middle Eastern countries; Sunday only in some places). Public holidays are excluded too — but whose? A UK company's bank holidays differ between England, Scotland and Northern Ireland; a US federal holiday isn't a state holiday everywhere; and a courier crossing a border may lose a day at each end. For deadlines that matter, the governing calendar should be named. Calculators need a holiday list for the right country and year, and the honest ones let you add your own.

How many working days in a year

A common year has 365 days: 52 weeks and one day, giving 260 or 261 weekdays (262 in some leap years). Subtract public holidays — 8 in England and Wales, 10–11 federal in the US, 9–13 across most of Europe — for 249–253 working days, and personal leave for the days actually worked (roughly 225–235 for a full-time employee with four to five weeks' holiday). That is the divisor that turns an annual salary into a day rate (Gross vs net salary: what comes off your pay, and how to compare offers) and a project budget into a duration (the Gantt chart).

Contracts, courts and SLAs

Legal drafting defines "business day" precisely — often "a day other than Saturday, Sunday or a public holiday in [place] on which banks are open for business" — and states whether periods run from the day after the triggering event. Court rules do the same: many civil procedure rules exclude the day of the event and, for short periods, weekends and holidays. Service-level agreements define business hours (say 9–5 in a named time zone) and count response time only within them, so a ticket raised at 4:55 p.m. Friday with a "4 business hours" target is due Monday morning. Read the definition clause before counting; when there isn't one, ask before relying on your count. Working across time zones covers the zone problem for global teams; the meeting planner the scheduling.

Calculating it

Forward: from a start date, add n working days, skipping weekends and listed holidays. Backward: the latest working day to start so that n working days end by a deadline. Between: count the working days from one date to another, inclusive or not. The calculator does all three with a holiday list for your country and shows the calendar so you can see which days were skipped. For dates alone, the date difference calculator and the day-of-week finder cover the rest; the week number tool names the ISO week the deadline lands in (ISO week numbers explained: why week 1 isn't 1 January and some years have 53 weeks).