dark o'clock 

When it's so late at night or early in the morning that it's dark out.

"Man, I stayed at work til dark o'clock yesterday" or "I woke up and it was still dark o'clock"

dark o'clock by kimber_kev August 27, 2005

dark o'clock in the morning 

The hours between midnight and dawn, when it's morning but it's totally dark and no one's up unless they absolutely have to be.

Go to bed early, hon. We have to catch the bus at dark o'clock in the morning to get there on time.

dark o'clock in the morning by 2011Grad August 11, 2010