"the evening or the day before a holiday, church festival, or any date or event: Christmas Eve; the eve of an execution."So tomorrow could properly be referred to as "Christmas Eve" all day long. Or you could call it "the day before Christmas" or "December 24th". Just don't call it "Christmas Eve Day"! Okay?
And if I hear anyone over the age of nine refer to today as "Christmas Eve Eve" I'm just gonna smack 'em!