What is a business day?

What is a business day?

A business day, also called a working day, is a day on which most banks, government offices, and financial markets are open for ordinary business. In most of the world a business day is one of Monday, Tuesday, Wednesday, Thursday, or Friday, with the public holidays of the country or region excluded; the count of "business days between" two dates is the count of such days under whichever inclusive-or-exclusive convention the calling system uses. The term is operational rather than calendrical: it picks out the days on which a deadline, a wire transfer, or a delivery actually moves forward in the working calendar of a particular country.¹

There is no international standard that fixes which days count as business days. The closest thing to one is the locale data maintained by the Unicode Consortium, the body that publishes the locale rules every major operating system reads to render calendars and date pickers. Its weekend-day data ships with two attributes per territory — weekendStart and weekendEnd — that record the calendar convention currently in use; the working week is everything else. The world default in that data is Saturday and Sunday as the weekend, with around fifteen territories carrying explicit overrides.¹ National labour law, banking law, and securities regulation each carry their own definitions on top of that calendar convention, and those definitions are what the operational use of "business day" actually rests on.⁴⁹

Which days are the working week, country by country?

The working week is Monday through Friday in the great majority of countries, including all of Europe, North America, Latin America, sub-Saharan Africa, South and Southeast Asia outside the Gulf, East Asia, and Oceania. The Unicode locale data records this five-day, Monday-to-Friday week as the world default, expressed as a Saturday-Sunday weekend.¹ In countries where the working week deviates from the default, the deviation is almost always tied to a religious rest day — the Muslim Friday or the Jewish Saturday — rather than to any administrative convenience.

In most of the Arab world the weekend is Friday and Saturday, and the working week therefore runs from Sunday through Thursday. The countries where the locale data records this convention include Algeria, Bahrain, Egypt, Iraq, Jordan, Kuwait, Libya, Oman, Qatar, Saudi Arabia, Sudan, Syria, and Yemen.¹ The convention is not ancient. Saudi Arabia kept a Thursday-Friday weekend until 2013, when a royal order moved it to Friday-Saturday with effect from 29 June 2013, citing better alignment with the working weeks of the country's regional and international trading partners.² The United Arab Emirates moved further still: from 1 January 2022 the federal government took Saturday and Sunday as its weekend, with Friday becoming a half-day for the public sector — making the United Arab Emirates the first country to introduce a national working week shorter than the global five-day standard.⁶

Two further variants exist. Israel takes Friday and Saturday as the weekend in the locale data, by way of the Jewish Sabbath, but the standard working week runs from Sunday through Thursday, sometimes extended to a half-day on Friday in services and government roles. The country's working-time legislation fixes the weekly rest period at not less than 36 consecutive hours and requires that period to include the Sabbath day for Jewish workers and the worker's customary day of rest for non-Jewish workers; a Sunday-to-Thursday working week satisfies the rule cleanly.³ Iran and Afghanistan stand outside the Friday-Saturday convention. Iran has a single-day weekend on Friday, with the working week running Saturday through Thursday; Afghanistan has a Thursday-Friday weekend, running its working week from Saturday through Wednesday.¹ Brunei is the lone outlier — its working week is Monday through Thursday plus Saturday, with Friday and Sunday off, the only national working week with a non-contiguous weekend in current use.

How do public holidays change which days count?

Public holidays are excluded from the business-day count, and most countries have an explicit rule for what happens when a holiday falls on a weekend. The default in much of the world is to observe the holiday on the nearest weekday — typically the following Monday — under what is variously called an in-lieu, substitute, or observed day. The rule is not folklore but legislation, and the exact form differs by country.⁴⁵

The United Kingdom has the rule written into its banking law. The Banking and Financial Dealings Act 1971 designates the bank holidays for England and Wales, Scotland, and Northern Ireland in its Schedule 1, and provides that any payment or act for which a person would be compellable on a bank holiday is treated as fulfilled if it is performed "on the next following day on which he is compellable to make or do it."⁴ Holidays falling on a weekend are observed on the next working weekday by force of the same provision; bank-holiday Mondays at the start of May and August are the most familiar consequence.

In the United States, the Federal Reserve Board publishes a holiday schedule of eleven named days that the Federal Reserve banks and the Board of Governors observe each year — New Year's Day, Martin Luther King Jr.'s birthday, Washington's birthday, Memorial Day, Juneteenth National Independence Day, Independence Day, Labor Day, Columbus Day, Veterans Day, Thanksgiving Day, and Christmas Day.⁵ When one of those holidays falls on a Sunday, all Federal Reserve offices are closed the following Monday; when it falls on a Saturday, the Reserve banks are open the preceding Friday but the Board of Governors is closed for the actual day.⁵ The split — Reserve banks open on a Friday, Board offices closed on a Saturday — is a recurring source of confusion for operational planning at year-end.

Most other countries write their substitution rules into a public-holidays act, a labour code, or a presidential decree. The clock.global holidays index records the official lists for every country covered, with the issuing source for each, and the country pages such as United States and United Kingdom carry both the actual holiday dates and the in-lieu observed dates.

What is a "banking day" in law?

A banking day is a narrower legal term than a business day, and the two are not interchangeable. Article 4 of the Uniform Commercial Code — the harmonised commercial-law statute adopted in some form by every United States state — defines a banking day as "the part of a day on which a bank is open to the public for carrying on substantially all of its banking functions."⁹ A Saturday on which a branch is open for retail deposits but not for check clearing is not a banking day in this sense; the statute's deadlines for processing items and giving notice run on banking days only.

The same article carries a second term that depends on the first. The midnight deadline — the latest moment a bank may take action on an item without losing its rights of recourse — is "midnight on its next banking day following the banking day on which it receives the relevant item or notice or from which the time for taking action commences to run, whichever is later."⁹ The deadline is one of the most-litigated provisions in commercial banking, and the precision of the "banking day" definition is what makes it operable: a bank cannot extend its own deadlines simply by remaining open on a weekend with reduced services.

Other jurisdictions carry comparable definitions. The Banking and Financial Dealings Act 1971 makes Saturdays, Sundays, and the days listed in its Schedule 1 non-working days for any obligation arising under bills of exchange and promissory notes; the rule has the same operational effect as the United States banking-day definition.⁴ In financial-market regulation the term "trading day" picks out a different set still, restricted to days on which a particular exchange is open — the New York Stock Exchange and Nasdaq each publish a calendar of holiday closures that is similar to but not identical to the Federal Reserve schedule, and equity trades therefore happen on a slightly different set of days than retail bank transfers.⁵

How do business days drive financial settlement cycles?

Securities-settlement deadlines are counted in business days from the trade date. Until 2024, United States equity trades settled two business days after the trade — the convention known as T+2. The Securities and Exchange Commission shortened the standard cycle to one business day — T+1 — by amending Rule 15c6-1 of the Securities Exchange Act, with all elements of the amended rule in force from 28 May 2024. The rule prohibits a broker-dealer from purchasing or selling a non-exempt security for settlement later than the first business day after the trade unless the parties expressly agree otherwise at the time of the transaction.⁷ An equity trade executed on a Wednesday now settles on the Thursday; one executed on a Friday settles on the following Monday, with intervening weekends and federal holidays advancing the settlement date by one banking day each.

The European Union has historically held equity settlement at T+2, harmonised across the bloc since 1 January 2015 by the regulation that governs its central securities depositories. In June 2025 the European Council and Parliament agreed to shorten the cycle to T+1, and the legislative timetable now targets 11 October 2027 as the effective date for the move; the United Kingdom and Switzerland are coordinating on the same date.⁸

The same business-day arithmetic governs operational deadlines outside the equity markets. Domestic wire transfers between United States banks settle on the same banking day if initiated before the cut-off; cross-border wires through the international interbank messaging network typically settle the following banking day in the receiving country, with both the sending and receiving country's holiday calendars affecting the timing. Letters of credit, demand for payment under bills of exchange, and the cure periods on commercial loan defaults are likewise quoted in business or banking days, with the underlying calendar fixed by the governing-law clause of the contract.⁹

How is the number of business days between two dates calculated?

The standard convention counts business days between two dates by including the end date and excluding the start date — five business days from a Monday lands on the following Monday, not the Friday — and skipping over weekend days and any public holidays observed in the relevant calendar. Off-by-one errors trace to the same place as date-arithmetic bugs in general: a function that returns the count of business days between two dates can mean "elapsed", "inclusive of both ends", "exclusive of both ends", or "exclusive of start, inclusive of end", and the four conventions disagree by up to two days for short windows.¹

For the common case of a Monday-to-Friday working week with no public holidays in the span, the formula is straightforward. Let n be the count of calendar days from the start date to the end date, exclusive of the start. The count of business days is then n minus the count of Saturdays and Sundays in that span — twice ⌊n / 7⌋ for the complete weeks, plus a small correction term that depends on which weekday the start date falls on. Real-world implementations skip the closed-form arithmetic and iterate over each day, looking up the country's holiday calendar for each candidate weekday — the path our business-days calculator takes, because it must support arbitrary weekend conventions and a per-country holiday list.

The ISO week date is a useful adjacent tool when the working week itself matters. The international standard for date strings numbers the seven days of the week Monday = 1 through Sunday = 7, so a date written 2026-W19-3 immediately tells the reader which working day of the week it falls on under the standard convention; the same date can be passed through a per-country weekend calendar to determine whether it counts as a business day in any given jurisdiction.¹

What are the common pitfalls?

Business-day arithmetic fails in predictable ways. Most production bugs trace to one of these patterns:

• Mixing weekend conventions. A pricing engine running in London cannot count business days in Riyadh by skipping Saturday and Sunday. The Saudi working week excludes Friday and Saturday, not Saturday and Sunday; a deal counted at "T+5 business days" in a London system will be one day off the date the Riyadh counterparty is operating against if the converter does not consult a country-specific weekend table.¹²
• Missing in-lieu observances. A holiday calendar that lists only the calendar dates of public holidays, without the substitute days for holidays falling on a weekend, will under-count the non-working days for those years. British 26 December 2026 Boxing Day falls on a Saturday in 2026, with the in-lieu observance moved to Monday 28 December under the Banking and Financial Dealings Act 1971; a calendar that hard-codes 26 December and stops there will mark the Monday as a working day.⁴
• Time-zone effects on the trade date. An equity trade matched at 03:00 UTC on a Tuesday is a Monday-evening trade in New York and a Tuesday-morning trade in Tokyo; T+1 settlement therefore lands on Tuesday in New York's calendar and Wednesday in Tokyo's. Settlement systems resolve the ambiguity by fixing a timestamp on the matching engine's local clock; the choice of clock is a non-trivial cause of cross-border settlement breaks.⁷
• Banking day vs. business day. A retail branch open on a Saturday is offering business hours but not a banking day in the legal sense. The Uniform Commercial Code's deadlines run on banking days only; if a deposit is presented on a Saturday opening, the bank's midnight deadline runs from the next banking day, not from the Saturday.⁹
• Half-days as full days. Christmas Eve and the day after Thanksgiving are partial trading days on the New York Stock Exchange — the exchange closes at 13:00 Eastern Time rather than 16:00 — but settlement systems still treat them as full business days for T+1 counting purposes. A countdown that excludes them as non-business days will undercount the settlement date by one day.⁷
• Locale-default weekend in user-facing tools. A calendar widget that uses the operating system's locale-default weekendStart and weekendEnd will show different shaded weekend cells to a user with their device set to Saudi Arabia than to a user with their device set to the United States. Tools that need to count business days in a fixed jurisdiction — for example, a deadline calculator on a United States court's website — must override the locale default to the jurisdiction's calendar.¹

Frequently asked questions