Business Days vs Calendar Days

Quick answer

A calendar day is any day shown on the calendar, including Saturdays, Sundays and bank holidays. A business day (also called a working day) is usually Monday to Friday, excluding weekends and public or bank holidays. The two measures can produce very different deadlines: a 5-calendar-day period that starts on a Monday ends on the Saturday, while a 5-business-day period that starts on a Monday ends the following Monday. In the UK, "working days" for most statutory deadlines (such as the Freedom of Information Act's 20 working day response period) mean ordinary weekdays, and the definition of a bank holiday is set out in the Banking and Financial Dealings Act 1971.

What a business day is

In the UK there is no single universal legal definition of a business day, which is why contract wording matters. The common understanding is that a business day is a day when banks and most businesses are open: normally Monday to Friday, excluding bank holidays. Weekends (Saturday and Sunday) are not business days, and neither are the eight statutory bank holidays in England and Wales. Scotland and Northern Ireland have slightly different bank holiday calendars, so the same date range can resolve to a different number of business days depending on jurisdiction.

Some contracts and regulations define "working day" more precisely. For example, the Freedom of Information Act 2000 defines a "working day" in section 10(6) as any day other than a Saturday, a Sunday, Christmas Day, Good Friday, or a day which is a bank holiday under the Banking and Financial Dealings Act 1971 in any part of the United Kingdom. That means a bank holiday anywhere in the UK pauses the FOI clock even if it is not a holiday where the public authority is based.

What a calendar day is

A calendar day is every day, with no exclusions. A period measured in calendar days runs continuously across weekends and bank holidays. Many consumer and data-protection deadlines are measured in calendar days or calendar months. For example, the one-month deadline for responding to a subject access request under Article 12(3) of the UK GDPR is a calendar month, not a number of working days, so weekends and bank holidays count towards it. The 14-day cooling-off period for most online and off-premises consumer contracts is also measured in calendar days under the Consumer Contracts (Information, Cancellation and Additional Charges) Regulations 2013.

Where working days are used

Working-day measures appear throughout UK regulation and business practice. Common examples include:

• Freedom of information: public authorities must respond to an FOI request within 20 working days (Freedom of Information Act 2000, section 10).
• Court and tribunal deadlines: many civil procedure and tribunal directions specify a number of working days or business days.
• Payment and delivery terms: business contracts often promise delivery or payment "within X business days".
• Customer service commitments: firms may promise to answer a complaint or refund "within X working days".

Because working days exclude weekends and bank holidays, the same nominal number of days can span a much longer calendar period. Ten business days is typically about two calendar weeks (14 calendar days) because each week contributes five business days and two non-business weekend days.

Where calendar days are used

Calendar-day measures are common where the law wants a simple, continuous period that is harder to dispute. Examples include:

• Subject access requests: one calendar month (UK GDPR Article 12(3)).
• Cooling-off periods: 14 calendar days for distance and off-premises sales (Consumer Contracts Regulations 2013).
• Notice periods: statutory and contractual employment notice is usually expressed in weeks or months, which run as continuous calendar periods.
• Section 21 eviction notice: at least two calendar months (Housing Act 1988).
• Invoice payment terms: "net 30" typically means 30 calendar days, though some businesses specify business days instead.

Bank holidays and the UK working week

England and Wales have eight statutory bank holidays each year: New Year's Day, Good Friday, Easter Monday, the early May bank holiday, the spring bank holiday, the summer bank holiday, Christmas Day and Boxing Day. When a bank holiday falls on a weekend, a substitute day is usually taken on the following weekday. Scotland has nine bank holidays (including 2 January and St Andrew's Day), and Northern Ireland has ten (including St Patrick's Day and the Battle of the Boyne). This is why a "UK business day" calculation should always state which nation's holiday calendar applies.

Our 2026 UK bank holidays and business days calculator applies the correct holiday list for England and Wales, Scotland, or Northern Ireland so you can see exactly how many working days sit between two dates.

Worked example: the same five days, two different answers

In the third row the spring bank holiday (Monday 25 May 2026) extends the period further, showing why you must account for bank holidays as well as weekends when counting business days. Use the business days calculator to check a specific range without hand-counting.

Step-by-step: deciding which measure to use

1. Read the source. Find the exact wording in the legislation, contract, policy, or service terms: does it say "days", "calendar days", "working days", or "business days"?
2. Identify the holiday calendar. If working days are involved, confirm which nation's bank holidays apply.
3. Count forward. For business days, skip weekends and the relevant bank holidays; for calendar days, count every day.
4. Watch the start day. Check whether the day the clock starts is day zero or day one, and whether the deadline can fall on a weekend or holiday (many periods roll forward to the next working day).
5. Verify with a calculator. Run the dates through the business days calculator or the relevant deadline calculator to catch arithmetic slips.

Key takeaways

• Calendar days include weekends and bank holidays; business days exclude them.
• UK statutory "working days" (for example under the FOI Act) mean weekdays excluding bank holidays, as defined by the Banking and Financial Dealings Act 1971.
• Bank holidays differ between England and Wales, Scotland, and Northern Ireland.
• FOI uses working days; SAR and cooling-off periods use calendar days or months.
• Always confirm which measure and which holiday calendar the relevant rule or contract uses before calculating.

Related guides

• FOI 20 Working Days Explained
• Subject Access Request Time Limit UK
• Invoice Due Date Net Terms
• Excel WORKDAY Formula

References

• Banking and Financial Dealings Act 1971 (legislation.gov.uk)
• Freedom of Information Act 2000, section 10 (legislation.gov.uk)
• UK GDPR, Article 12 (legislation.gov.uk)
• Consumer Contracts (Information, Cancellation and Additional Charges) Regulations 2013 (legislation.gov.uk)
• GOV.UK - UK bank holidays