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Business Days, Weekends and Public Holidays
Why five business days is not five days, how to count working days by hand, and why public holidays make cross-border deadlines harder than they look.
Updated: 2026-10-19 · 5 min read
Contracts, delivery estimates and payment terms are usually written in business days. The phrase sounds precise and is not: it depends on which days your week runs, which country's holidays apply, and whether the count starts today or tomorrow.
What counts as a business day
In most of Europe and the Americas, a business day is Monday to Friday, excluding public holidays. In much of the Middle East the working week runs Sunday to Thursday. Some countries work a half day on Saturday, which is neither a full business day nor a weekend.
That difference alone can shift a five-day deadline by two days. Before counting, establish two things: which country's calendar governs the agreement, and whether the count starts on the day of the notice or the day after.
Counting working days by hand
Count whole weeks first. A span of five business days from a Monday reaches the following Monday, because Tuesday through Friday is four days and the second Monday is the fifth. The start day is not counted; the end day is.
For longer ranges, divide the calendar days by seven and multiply by five, then correct the remainder. A 30-day span contains four full weeks (20 business days) plus two leftover days, which may add zero, one or two business days depending on where the span starts.
Then subtract public holidays that fall inside the range and on a weekday. A holiday that lands on a Saturday changes nothing, because that day was not counted anyway.
Public holidays are the hard part
Weekends are the same every week. Holidays are not: they move, they differ by region within a country, and some are observed on a substitute day when they fall on a weekend.
China is a good example of why a fixed rule fails. The Spring Festival and National Day holidays shift each year according to the lunar calendar, and the government publishes adjusted working weekends — days that would normally be rest days become working days. No simple weekend-only rule can reproduce that.
Germany has regional holidays: Epiphany is a public holiday in Bavaria but not in Berlin. The United States has federal holidays that most employers observe and state holidays that they do not. A deadline that is valid in one office can be wrong in another.
Why this breaks global teams
When a supplier in one country promises “five business days” to a customer in another, at least three calendars are in play: the supplier's working week, the customer's, and any country in between that handles the shipment.
The practical fix is to convert the promise into an absolute date as soon as it is made, and to state which calendar was used. “Five business days from 12 October, UK calendar, so by 19 October” is unambiguous. “Five business days” on its own is an invitation to argue later.
What the calculator does and does not do
The business days calculator on this site counts weekdays only: Saturday and Sunday are removed, the start date is excluded, the end date is included, and the result is never negative.
It does not remove public holidays, because holiday calendars are country-specific and change every year. For a defensible deadline, take the weekday count from the calculator and then subtract the holidays that apply to the specific agreement.