Let me make this clear: “Christmas Eve” is not the same as “the day before Christmas”! Christmas Eve is the evening before Christmas. It starts when evening starts, be that 6:00pm, sunset, or whenever. It does not start at noon. If you say “Happy Christmas Eve”, I get to say “Not yet!” if it’s 2:33pm.
My dad’s a teacher, and my mom worked at a university, so they both had Christmas eve off. We had a long-standing party at our place for family and friends in the afternoon, with present opening that night, so for us, the whole day was Christmas Eve. Nyah.