What 'Business Days' Really Means in Contracts and SLAs

When a contract says “delivery within 10 business days”, that phrase is doing more work than it looks. It’s deceptively easy to miscount, especially across weekends, holidays, and time zones.

What is a business day?

A business day is normally any Monday through Friday that isn’t a public holiday in the relevant jurisdiction. It’s also called a working day in many contracts, an open day in financial markets, and a trading day when referring to stock exchanges.

The key parts of that definition:

Mon–Fri — Saturdays and Sundays don’t count.
Public holiday — varies by country and even by state, province or city.
Relevant jurisdiction — a UK contract typically uses UK holidays; a Saudi Arabian one uses the Friday/Saturday weekend.

The endpoint trap

The single biggest source of business-day disputes is whether the start day is included. “10 business days from Monday” can mean:

“Counting Monday as day 1, deliver by the next Friday.” (inclusive)
“Counting from Monday-end, deliver by the following Friday.” (exclusive)

Most contracts mean the exclusive version — i.e. the day the clock starts is not counted. But the only way to be sure is to read the contract carefully or use a definitions clause that states it explicitly. Our working days calculator lets you toggle between inclusive and exclusive endpoint behaviour for exactly this reason.

Holidays that complicate counting

Holiday lists are surprisingly slippery:

Federal vs. state: in the US, a Memorial Day deadline is a federal holiday but local courts may still be open.
Bank vs. public: in the UK there is technically no “public holiday”, but bank holidays are widely treated as business non-days.
Religious vs. civil: in many countries Eid, Diwali or Lunar New Year run on lunar/solar-lunar calendars, so the dates shift each year.
Substitute days: when a holiday lands on a weekend, many countries observe it on the nearest weekday — sometimes Friday, sometimes Monday.

A general-purpose calculator can’t bake all of that in without becoming wrong for most users. We chose to let you paste your own holiday list — accurate for your jurisdiction, valid for the year you actually need.

Common formulas to memorise

N business days from a start date: count Mon–Fri, skip holidays, return the Nth date.
Business days between two dates: subtract weekend days and holidays from the total range.
Working hours estimate: business days × hours-per-day (typically 8).

When not to use business days

Notice periods in property leases are sometimes calendar days, not business days.
Statute of limitations in many jurisdictions runs on calendar days only.
Health-care timelines (e.g. “see your doctor within 14 days”) almost always mean calendar.

When in doubt, your contract or your lawyer wins — never the calculator.

Quick example

Imagine a 7-business-day SLA starting on a Friday with a Monday public holiday. Counting exclusively:

Day 0  Friday      → start
Day 1  Monday      → holiday, skip
Day 1  Tuesday     ✔
Day 2  Wednesday   ✔
Day 3  Thursday    ✔
Day 4  Friday      ✔
Day 5  Monday      ✔
Day 6  Tuesday     ✔
Day 7  Wednesday   → due

Without the holiday adjustment you’d answer Tuesday — a full day early.

Tools

Use the working days calculator to test your assumptions, and the date add/subtract calculator for “N business days from today” questions.