The times of day when you realize that it's too early or too late to call friends and/or family. "Hoot" is an acronym that stands for "hold off on telephone". "Hoot" also suggests times of the day when owls are active and hooting.
Adam: Do you think it's okay to call Barbara and Debbie for a hike up in the Catskills?
John: I dunno, Adam, I think it's hoot time for Debbie. She works a graveyard shift and usually hits the sack first thing when she gets home.