When it comes to recorded, nightly television shows, which ones are actually delayed for the benefit of more westerly viewers?

Take for example, a hypothetical show, Podunk, CSI, which is shown at 9:00 PM in New York. Typically viewers in the central time zone would see this show simultaneously, which would be at 8:00 PM in their time zone. But the Mountain and Pacific time zones actually have their broadcasts delayed. Nobody's watching Podunk, CSI at 7:00 PM Mountain or 6:00 PM Pacific. Instead, the broadcast on NBC affiliates in those times zone is delayed so that the show is aired during "prime time."