When a public holiday lands on a weekend, countries do not do the same thing. Importers of generic iCal feeds flatten those differences into a single “observed Monday,” which is why a London Monday is closed, a Tokyo Wednesday is closed, a Beijing Saturday is unexpectedly open, and a Seoul Tuesday is closed for a reason that does not appear on last year’s calendar.
Japan: furikae kyujitsu and kokumin no kyujitsu
If a national holiday falls on Sunday, the next day that is not already a holiday becomes a holiday. In 2026 Constitution Memorial Day is Sunday 3 May; Greenery Day and Children’s Day occupy Monday and Tuesday, so the substitute rolls to Wednesday 6 May. Separately, a weekday trapped between two national holidays becomes a citizens’ holiday. That is why 22 September 2026 is off between Respect-for-the-Aged Day and the Autumnal Equinox. Neither rule asks anyone to come to work on a Saturday.
United States: “observed”
If a federal holiday falls on Saturday, Friday is typically the observed day for federal employees; if it falls on Sunday, Monday is observed. Independence Day 2026 is Saturday 4 July, so Friday 3 July is the observed federal day. Private employers copy this, ignore it, or invent a floating day. State holidays are a different list.
Korea: substitute public holidays
대체공휴일 applies to named holidays when they collide with a weekend or, in some years, with another holiday. The list of which holidays qualify has been expanded by statute and is not identical to Japan’s mechanical Sunday rule. Children’s Day on 5 May 2026 is a Tuesday and does not need a substitute; Liberation Day on Saturday 15 August does, which is why Monday 17 August appears on Korean calendars.
United Kingdom: bank holidays that move
If Boxing Day is a Saturday (26 December 2026), the substitute is usually the following Monday. Good Friday and Easter Monday do not move — the Christian calendar already placed them. Scotland and Northern Ireland keep additional local days. “Bank holiday” is not a statutory right to paid leave for every worker; it is a banking and public-office closure that employment contracts then reference.
China: a swap, not a shift
Tiaoxiu borrows a weekend and attaches it to the festival, then makes a different weekend into a working day. Rest is conserved, not shifted by one. That is why foreign feeds miss makeup Saturdays. The full arithmetic is in how tiaoxiu works.
Singapore, Hong Kong and others each have their own weekend-collision notes on the labour-ministry pages. If you maintain one “observed” column for the whole region you will schedule people onto a workday or off a workday they do not have. Build the exception into the coverage calendar, not into a spreadsheet footnote nobody reads.
A one-line test for any imported feed
Open 4 May 2026. If your feed shows a single label for the whole world, throw it away. That Monday is Labour Day leftover in China, Greenery Day in Japan, the Early May bank holiday in England and Wales, and Coronation Day in Thailand. A correct feed emits four rows or four calendars. This site stores the same split: date plus territory plus name. That is the only structure that survives a year when several unrelated holidays collide.
Teach the team the name of the local rule — furikae, observed, 대체공휴일, bank-holiday substitute, tiaoxiu — rather than a single “moved to Monday” habit. The name tells you whether a Saturday might unexpectedly be a workday. That is the mistake that costs a release, not the colour of a calendar cell.