In a sense, Sonnet 73 doesn't really have a setting. The speaker never tells you that he is standing in a particular place, or living at a particular time. Still, the speaker's mind does take us to several distinct places: first, the countryside (quatrain 1), where we see a tree with facing down the oncoming winter. Then, it's the countryside again (quatrain 2), but this time with our focus directed toward the horizon where we see the last light of the sun that has already set. Next, we are brought indoors (quatrain 3) where we see the last embers of a fire dying in the hearth. It's part of the couplet's effect that it doesn't give you any real clue about where it might be taking place. This lets you focus on what is really important here: the relationship between two people, the speaker and the listener.