In SC you can shoot 1 hour before official sunrise. You can't shoot 1 hour after official sunset. I like to be in the stand 1 1/2 hour before official sunrise. What is official sunrise? Ask the US Naval Observatory. They are the official timekeeper for the US Government.
http://tycho.usno.navy.mil/
Here is a sunrise/sunset calculator from their website.
http://aa.usno.navy.mil/data/docs/RS_OneDay.php
You enter the date you are interested in, the state and town. Alternately you could enter the Lat. and Long. for the exact moment of sunrise at your stand.