The act of consuming mass quantities of alcohol during the daytime - e.g. the hours between waking up and roughly 5pm.
E: "Dude, what's up?"
J: "Duuude, I'm so hammered!"
E: "It's 5 pm, man - didn't you go to work today?"
J: "Naw, called in sick. Me and Brett have been day raging over at his place since like 10am."
E: "Well, I guess you can't drink all day long if you don't start in the morning."
"The beer I had for breakfast wasn't bad, so I had one more for dessert." - Johnny Cash, 'Sunday Morning Coming Down'