Dec. 31st, the day before Jan. 1st. On that night you are supposed to get drunker than you have the whole year, in order to usher it out for the next year of drinking.
If you don't get fucked up on new year'seve, Ima kill you.
He waited until Christmas EveEveEve before starting his Christmas shopping. On Christmas Eve Eve, he had other plans. Typically, they opened their gifts on Christmas Eve, not Christmas Day.