"If I could, I would surf the internet all day long."
Translation:Se mi povus, mi retumus la tutan tagon.
Sorry for all the questions, but why does "tutan tagon" take the accusative -n? Could I say, "Se mi povus, mi retumus dum la tuta tago"?
the accusative can be used instead of the preposition. In this case it is instead of tra or dum.
Your sentence is the "more original" one and totally fine. Please keep using it!
The -n is sometimes used for durations. I suppose that there is more information on this in the tips and tricks somewhere.
My dictionary says that “tra la tuta tago” should also be accepted. Are those two constructions (with “tra” and with “dum”) any different?
Usually "dum" means "while" in a strictly temporal sense, so referring to some sort of temporal relation or simultaneousness.
On the other hand "tra" usually means "trough" in a strictly "through some sort of material"-sense like through a wall or trough a cake.
So it seems to me, that "tra la tago" is more like some metaphorical usage. It is understandable but I would recommend "dum la tago" as long as you are not doing poetry or something.