NOCHEBUENA is the “good night” before Christmas.
Here in Argentina it’s also when Santa comes–the kids staying up until 12 when it switches to actual Navidad and a family member dressed as Santa appears pillow-stuffed and possibly wine-drunk at the door. Presents are distributed. Everyone stays up all night. This is the answer for those who ask how Argentine kids seem to have no bedtimes but can still get up and function each morning. Like most things it comes down to imagination.