The setting of "The Listeners" by Walter de la Mare is within a forest. We know that the horse grazed on grasses growing on "the forest's ferny floor" and that a bird flew out of a turret. The sill of the house at which the traveller stops is "fringed" in leaves, and a "leafy sky" is above his head. The setting never changes, and although the traveller tries to get someone to allow him inside, he is left alone at this solitary house deep in the forest, details that point to its being overgrown and very much remote.
The time is night. Moonbeams dance on the stairs and light up the door upon which the traveller knocks. The sky is filled with stars as he waits for someone to answer his call. The only other context clue that could possibly align to a time is that the traveller rode in on horseback, so one could surmise that the poem is not modern (and, indeed, it was written over a hundred years ago).
However, it is possible that one could ride in on horseback to a remote, isolated house even today, so this alone isn't enough to date the poem to a specific time period. The when is left open enough for the poem to transcend any particular time period.