Bank holiday substitute days: which dates should you count?

·Published: 16 September 2026

A bank holiday substitute day is a weekday used when a holiday falls at the weekend. The celebration keeps its familiar date, while the substitute affects which weekdays are excluded from a working-day count. Christmas 2027 makes the distinction particularly clear: Christmas Day is Saturday 25 December and Boxing Day is Sunday 26 December, followed by substitute bank holidays on Monday 27 and Tuesday 28 December. To count correctly, first decide whether you need calendar days, working days or the dates of the celebrations themselves.

The celebration date and the substitute weekday

Christmas Day remains 25 December, whatever day of the week that date happens to be. A substitute bank holiday on 27 December does not move Christmas dinner, the religious festival or the anniversary on the calendar. Likewise, Boxing Day remains 26 December. Keeping those dates separate from their substitute weekdays explains why a calendar can show the named occasion at the weekend and another entry relating to it during the following week. The entries describe different aspects of the same holiday.

For a working-day calculation based on Monday to Friday, Saturdays and Sundays have already been left out. A celebration falling on one of those days therefore cannot remove another weekday from the total by itself. The substitute supplies the weekday exclusion. This is why subtracting every holiday-related calendar entry from a weekday total gives the wrong result: a weekend date has no place in that starting total. Each date should be excluded once, even when more than one reason for excluding it applies.

Christmas 2027: two holidays, two substitutes

The Christmas pair needs to be considered together because the two celebrations occupy consecutive dates. In 2027, both fall at the weekend, so the substitute bank holidays occupy the following Monday and Tuesday. Christmas Day and Boxing Day are observed across England, Wales, Scotland and Northern Ireland, making this December example applicable throughout the United Kingdom. There are four consecutive dates to mark, but only two of them would otherwise be weekdays in a Monday-to-Friday count. Their roles are as follows:

• Saturday 25 December 2027: Christmas Day; already excluded as a Saturday.
• Sunday 26 December 2027: Boxing Day; already excluded as a Sunday.
• Monday 27 December 2027: the Christmas Day substitute bank holiday; exclude this weekday.
• Tuesday 28 December 2027: the Boxing Day substitute bank holiday; exclude this weekday too.

For someone whose normal working pattern excludes weekends and bank holidays, that produces a four-day break from Saturday through Tuesday. It does not mean four bank holidays should be deducted from an existing weekday total. Two dates belong to the normal weekend and two are substitute weekdays. Wednesday 29 December is the next working day under that counting convention. An organisation may remain closed for longer, but that additional closure is a separate matter and should not be silently included in the bank holiday calculation.

A worked count across the Christmas break

Take the period from Monday 20 December to Friday 31 December 2027, including both endpoints. It contains twelve calendar days. Two are weekend days, Saturday 25 and Sunday 26 December, leaving ten weekdays. Excluding the substitute bank holidays on Monday 27 and Tuesday 28 December leaves eight working days. This calculation assumes a Monday-to-Friday week and excludes bank holidays; it does not include annual leave or any additional Christmas closure. Stating those assumptions makes the total useful to somebody checking the same period.

You can also check the result by listing the dates that remain. Monday 20 to Friday 24 December contribute five working days. Wednesday 29, Thursday 30 and Friday 31 December contribute another three. Together they make eight. If you started with ten weekdays and subtracted 25, 26, 27 and 28 December, you would obtain six, because the weekend had effectively been removed twice. The two methods should agree: either count the eligible dates directly or subtract only exclusions that are present in your starting set.

A calendar-day count answers a different question. All twelve dates in that inclusive period remain calendar days, regardless of weekends or bank holidays. A countdown to Christmas Day still ends on 25 December, while a reminder for the Christmas substitute bank holiday points to 27 December. Also distinguish an inclusive range from elapsed time between two dates: including both endpoints adds a date that an elapsed-day calculation does not count. Choosing the counting convention before doing the arithmetic prevents confusion unrelated to the holiday itself.

Applying the rule to other dates

The paired pattern changes with the weekdays. When Christmas Day falls on a Friday and Boxing Day on a Saturday, Christmas Day is itself a weekday holiday and the Boxing Day substitute follows on Monday 28 December. When Christmas Day is a Sunday, Monday 26 December is already Boxing Day, so the Christmas substitute falls on Tuesday 27 December. In each case, consider both holidays before deciding which weekdays to exclude. Treating every weekend holiday as an isolated instruction to remove the following Monday can overlook the second holiday.

Elsewhere in the year, the relevant national calendar also matters. Scotland observes 2 January as well as New Year's Day, so it has another pair of neighbouring holidays to consider. England, Wales and Northern Ireland do not share that second January holiday. Conversely, a holiday defined as a Monday, such as the spring bank holiday, already falls on a weekday and does not need a weekend substitute. For any period, identify the applicable holidays, mark their weekday dates or substitutes, and exclude each affected date once. Keep any personal leave or additional closure separate from that calendar count.