There's some strange stuff going on with time in "Kubla Khan." When exactly does this poem take place? The Kubla Khan who actually lived belongs to the past, but is Coleridge recalling the Kubla Khan of the past, or someone who transcends our linear notion of time? If you are having a vision, are you looking backward or forward? Are you outside time? Whether or not these questions have answers, it's evident that different understandings of time is a major theme of the poem.
In "Kubla Khan" Coleridge moves backward and forward in time, making it impossible to tell exactly when any one event takes place. He does this in order to recreate the feeling of a dream, where time doesn't have a fixed meaning.