I've gone in as late as 9:00AM for an all day sit (to keep from bumpind deer out).....and as "early" as 3:30AM (went straight from a night out and the hot tub with the wife.....to the shower and then to stand....lol

).
I've got a spot I HAVE to go into, early. Early meaning at least 1.5hrs before shooting light (get ready Matt and Rob

).
Early season....it's getting to be shooting light here around 6:20 or so....maybe a little later (I'm basing this off NOT being in the woods). We'll go into one spot around 5:00AM. Other spots....they're new to me. We'll likely err on the side of caution there, too.....and go in at the same time.
Since we'll be walking to most of these spots....but climbing, also.....we'll be up at 4:00AM. I live within 2 miles of everywhere I hunt.