Ovid's poem ends with three surprising moments. The first surprising moment is the deification or "apotheosis" of Julius Caesar. (Even though it's a mouthful, "apotheosis" is a good word to know; it means "turning into a god," and crops up a lot in captions in books of pictures from Roman history. The Romans have a lot of pictures of people, usually emperors, turning into gods.)
The second surprising moment is when Ovid tells us what Julius Caesar did is nothing compared to what the Emperor Augustus, who was alive when Ovid wrote the poem, has done, and will do. Way to flatter your boss, Ovid. This flattery seems especially over the top given that Ovid's poem begins with the creation of the universe. It's like he's saying, "All of history was only building up to this moment when you, Augustus, finally come in to your own, and would you mind giving me some extra vacation time?" As it turns out, that's exactly what Augustus did, if by "vacation time" you mean "banishment to the Black Sea."
Why did he do that? No one knows – but maybe it's connected to the third surprising moment at the end of Ovid's poem. This is when he says that he himself, by writing the poem, has risen to a level of awesomeness beyond even the stars – and thus beyond Julius and Augustus Caesar. He also says that, through his poems, he will live forever. In this way, Ovid's poem covers the entire extent of time, from the beginning of the universe to its end.