Present Continuous Past(s)

Dan Graham's Present Continuous Past(s) is an installation piece where past and present, occur at the same time. A room is set up with a camera, a large monitor on one wall and a mirror on the other walls. The camera displays on the monitor what is happening in front of it, which is usually viewers. However the footage is delayed eight seconds. So people who are observing watch as the past and present happen at the same time. A viewer is watching footage that happened in the past in the present. So what defines the past and present when the video is being watched in the present, but has actually happened in the past? It would be interesting to see this piece in person.

Shanken, page 106.