Along the same vein… how are public holidays supposed to be handled? Do those always start and finish at midnight UTC, even if midnight UTC happens to be right

Along the same vein… how are public holidays supposed to be handled? Do those always start and finish at midnight UTC, even if midnight UTC happens to be right during the middle of the solar day (and everybody's waking hours)? Or does every place define a specific time (aligned to solar midnight or some other suitable point during the night) for when holidays are supposed to start and end, which is basically reintroducing timezones through the back door?