A replacement day off, given because the holiday itself fell on a day you were not working.
A day in lieu is a substitute granted when a holiday falls on a day an employee was not going to work anyway — a weekend, or a rostered day off — or when they worked through it.
It is close to substitution and not the same thing. Substitution moves the public holiday itself, for everyone, by rule. A day in lieu leaves the holiday where it is and gives an individual a different day, which may be chosen rather than fixed.
The distinction matters operationally because the two produce different absence patterns. A substituted holiday empties the office on a known date; days in lieu scatter across the following weeks and appear in no calendar at all.
Substitution moves the holiday for everyone, by rule and on a known date. A day in lieu leaves it and gives an individual a replacement, often of their choosing.
A bridge is an extra day taken to join a holiday to a weekend. A day in lieu replaces a holiday that was lost to one.
See also substitution · bridge day · public holiday · rest day
We hold this as not held as a distinct field — in-lieu entitlement is an employment fact, not a calendar one. See what we hold.