I dunno, maybe it's different with everyone. BodyOPUS states 48 hours, but a lot of people only do 24-36 hours. Some carb-up for 12 hours, but they do this every 4 days or so, not every 7.
I guess Friday when you do your depletion workout, which, I will assume, will be in the afternoon, carb up until Saturday night. Then on Sunday, switch back to no carbs.