"Legal shooting time" in TN is 30 mins before legal sunrise. But if it's a clear, cloudless day you can safely see clearly enough to shoot in most open areas 10-15mins before that. I prefer to be IN the stand, seated and crap put up and ready for the hunt at LEAST 15 mins before that and usually 20-30 mins. So that has you in the stand 1-1.5 hours before legal sunrise but like I said, you're really only "in the dark" about halfhour at most.
Same thing goes for sunset as well, 30 mins after usally means 10-15mins later before it's just to dark to tell an 8ptr from a 9ptr at 150yds through the brush.