Día de San Esteban.

No such thing as Boxing Day here, but instead it's St. Stephen's Day.
Stephen is the patron saint of deacons, headaches, horses, coffin makers, and masons. He is often represented carrying a pile of rocks or with rocks on his head. St Stephen's Day is 26th December and it is name checked in the Christmas carol Good King Wenceslas.  He was a deacon in the early Christian church and cared for the poor. Stephen was stoned to death by the Jewish council in Jerusalem after he condemned them for murdering the Messiah.