Counting working days

What counts as a working day

Monday to Friday. Saturdays and Sundays are skipped, and every other day counts — including public holidays, which the calculator does not know about and says so.

Counting a stretch and counting forward are different sums

This is the part that trips people up, and it is not a rounding difference — it is a whole day.

Both are correct answers to different questions. "We will respond within five working days" is the second one: the clock starts the day after. "The project ran Monday to Friday" is the first. The business days calculator does whichever you pick, and shows the dates either way so you can see which one you got.

One consequence worth knowing: a start date that falls on a weekend has no working days of its own to give up, so nought working days and one working day from a Saturday are both the Monday.

Subtracting, for when the deadline is fixed

If something has to be finished on a date, subtracting tells you the last day you can start. Ten working days before 25 December is 11 December — and counting back by hand is where people lose a day, because two weekends are in the way rather than one.

Business days and payment terms

Net terms are normally calendar days: Net 30 means 30 days, weekends included, unless the agreement says otherwise. Working days turn up in the other clauses — notice periods, response times, delivery windows, and terms written as "within 10 business days". If yours says business days, this is the count it means; if it says Net anything, it almost certainly does not. How due dates are counted covers the Net and end-of-month rules.

“Within five working days” is ambiguous

It is the most common phrasing in a contract and it does not say when the clock starts. If you are asked on Monday for something within five working days, that is Friday if Monday counts and the following Monday if it does not. Both readings are held sincerely, usually by the two people on either side of the same sentence.

The fix is to write the date rather than the count. “By Friday 25 September” cannot be read two ways. Where the count has to stay — because it is a standing term rather than one job — say which end is included: “five working days, not counting the day of the request” is four extra words that remove the entire argument.

Holidays are the part no calculator knows

Weekends are the same everywhere this is worth counting. Public holidays are not: they depend on the country, often on the region inside it, and on the year, and several move around the calendar. A tool that guessed would be confidently wrong somewhere, which is worse than being silent.

So the practical approach is to count the weekends automatically and subtract the holidays by hand, from whichever calendar actually governs the agreement — which is the payer's, not yours, if the question is when money arrives. A deadline that falls inside somebody else's long weekend is a deadline that was never going to be met.