Crepuscular is related to twilight, that time of the day that is neither night nor day, dark nor light.

Last night a few of us (Corinne, Shane, Jed, Darren, Angi, Mark, Heather, myself) were joking around about how tired Darren was from the torturous hours at KB during the holiday season. I told him that he's obviously not nocturnal, since he was so tired at night. He said, "I'm no better during the day," so I told him that he's not nocturnal or diurnal! Jed pointed out that the only alternative (other than "dead") is crepuscular.

We then decided that Darren is a pessimistic crepusculant: he's not awake for an hour or two, he's just exhausted for most of the day.