I'm not sure, but I would think 3-4 days would be fine. You got to think that in the wild, in Fla at least, when we have heavy storms, it's overcast for days if not a week. Especially during Hurricanes. There's a little daylight, but not much in the way of penetrating light. You will have some light on the tank, just by the ambient light in the room during the day.
Everything may not like it too much, but I think you'd be fine for 4 days, if necessary.