“Reply within 10 days.” “Notice of four weeks.” “Payment due within 14 working days.” Phrases like these look precise, but two people can read them and arrive at different dates, usually because of working days versus calendar days, or whether the first day counts. This guide explains how to read a deadline carefully and where the common traps are.
This article is general information, not legal advice. Rules on deadlines and notice periods vary by country, industry and contract, so always check the document itself and, where it matters, the relevant law or a qualified adviser.
Calendar days
Calendar days are every day on the calendar: weekdays, weekends and public holidays alike. Ten calendar days from a Monday is the Thursday of the following week, whatever falls in between.
Working days
Working days (also called business days) leave out weekend days and, usually, public holidays. Ten working days from a Monday, with a Saturday–Sunday weekend and no holidays, lands on the Monday two weeks later.
The catch is that “working day” has to be defined. Which days are the weekend? Which holidays? Holidays in which country or region? A well-drafted contract answers these questions in a definitions section. If yours does not, ask.
How to read a deadline
When you see a deadline, work through these questions in order.
1. What kind of day?
Look for the words “calendar”, “working”, “business” or “clear”. If the document just says “days”, check its definitions section. If there is no definition, do not assume. The meaning can depend on the type of document and the law that governs it.
2. When does the clock start?
Common starting points include:
- the date a document is signed,
- the date it is sent,
- the date it is received (which may be deemed to be a set time after sending),
- the date of an event, such as delivery of goods.
A deadline that runs “from receipt” can end on a different date from one that runs “from the date of this letter”.
3. Does day one count?
This is the most common source of off-by-one errors. Many rules start counting on the day after the triggering event, so the event day is “day zero”. Others count the event day itself. Some documents use “clear days”, which usually means that neither the first day nor the last day is counted.
There is no single worldwide rule. Check the wording, and if it is unclear, work to the earlier possible date.
4. What if the last day is not a working day?
If a calendar-day deadline ends on a weekend or public holiday, some rules move it to the next working day, some move it earlier, and some do not move it at all. Contracts sometimes include a clause dealing with exactly this. Do not assume you get the extra day.
5. What time of day?
“By 10 June” might mean the end of that day, the close of business, or a specific time stated elsewhere. Time zones matter too if the other party is in another country.
A worked example
Suppose a contract says a supplier must respond “within 5 working days of receipt”, the request is received on Monday 2 November 2026, the weekend is Saturday–Sunday, and the receipt day does not count.
- Tuesday 3 November – day 1
- Wednesday 4 November – day 2
- Thursday 5 November – day 3
- Friday 6 November – day 4
- Saturday and Sunday – skipped
- Monday 9 November – day 5
The deadline is Monday 9 November. If the contract instead said “5 calendar days”, the deadline would be Saturday 7 November, and you would then need to check whether a weekend end date moves.
If a public holiday fell on one of those weekdays, the working-day deadline would move one day later for each holiday.
Notice periods
Notice periods in employment and tenancy agreements are often expressed in weeks or months rather than days, which brings its own questions: does a month run to the same date in the following month, and does notice start on the day it is given or the next day?
Minimum notice periods may also be set by law, and the law may differ from what a contract says. Your contract, your employer’s HR team, an official government advice service or a qualified adviser are the right places to confirm what applies to you.
Common pitfalls
- Assuming “days” means working days. Unless the document says so, it may not.
- Using the wrong holiday list. A deadline governed by one country’s rules may use that country’s holidays, even if you are elsewhere.
- Forgetting regional holidays. Some holidays apply only in certain states, provinces or nations.
- Leaving it to the last day. Build in a margin for post, systems and time zones.
Checking your dates
For working-day deadlines, a tool helps avoid miscounting. The working days calculator can add working days to a date or count them between two dates using public holidays for 41 countries and different weekend patterns. When adding days it never counts the start date, which matches the “receipt day does not count” example above. When counting between two dates, use the “Include the start date” and “Include the end date” tick boxes to match the wording you are working to. Use it as a check, then confirm the result against your contract and the official holiday calendar.