About United Kingdom's Public Holiday Calendar
Most English and Welsh "bank holidays" are tied not to a fixed calendar date but to a specific Monday of the month (for example, the first and last Monday of May), so the exact date shifts every year.
When a bank holiday falls on a weekend, a substitute weekday is designated — in 2026, Boxing Day (December 26) falls on a Saturday, so Monday, December 28 is observed as the public holiday instead.