crack ass of dawn 

The early morning light of day. Too early to wake up especially after an all nighter.

the guy next door decided to mow his lawn at the crack ass of dawn, doesn't he know its Sunday?

crack ass of dawn by ravenlocks July 1, 2009

ass-crack of dawn

really early in the morning.

I had a flight to catch, so I had to wake up at the ass-crack of dawn.

ass-crack of dawn by kristiealexis January 13, 2008

ass crack of dawn 

Redonkulously early in the morning. Often it is still dark out. Commonly used when one must wake up early after a night of drinking, or getting up to go on a trip. Also can be referred to "Oh dark hundred"

Person 1: "Dude, what time do we have to get up tomorrow?"
Person 2: "The freaking ass crack of dawn."

ass crack of dawn by K.Spence June 11, 2006