"I will work that afternoon."
Translation:Mi laboros tiun posttagmezon.
Why is this accusative? That afternoon is not the thing I'm working, it's when I'm working.
I imagine that the accusative is being used as a means to indicate the complement of time. However, wouldn't that be ambiguous with a sentence that referred to one working on some afternoon (as in preparing an event?). Would there be any difference? Thanks.
A sentence can have an accusative as a direct object and another for the time. Normally it is clear form the context which is which. If there is any doubt you can put the time in an adverb.
Mi preparos tiun vesperon tiun posttagmezon.
Mi preparos tiun vesperon posttagmeze.
tio(n) is an unnamed thing that is known only by the context described or the speakers' surroundings. It never takes a "complementary noun". tiu(n) is a specific thing that is named or a person, and often takes a complementary noun.
Oh , this time I am happy I speak portuguese :) , We have different words too... Well, tiu - aquele, aquela ;tio - aquilo. So it can't be " tion" there, only "tiun" , It hard to explain it for an english speaker hahah , Spanish has words for this too " tiu - aquel, aquella " ; tio - aquello
Tiu is used with a noun (tiu pomo=that apple) Tio is used without a noun (tio=that [thing])