Why is Jimmy Kimmel always a rerun on Thursday? The guides usually don`t list it as a rerun, but it always is.

I just noticed this a couple months ago, the abc website usually lists TBD, which implies it is a repeat. But he did have Leann Rimes a month or so ago on a Thursday and it was a new episode. None of the late night shows actually work 5 nights a week, Letterman usually tapes his Friday show another night, and sometimes tapes 2 shows together, which means he would only work 3 nights. Conan is always a repeat on Mondays.