Most feature movies shown during the prime time and early overnight hours (8:00 p.m. to 2:30 a.m. Eastern Time) are presented by film historian Robert Osborne (who has been with the network since its 1994 launch, except for a five-month medical leave from July to December 2011, when guest hosts presented each night's films) on Sunday through Wednesday evenings – with Osborne only presenting primetime films on weekends – and Ben Mankiewicz presenting only late evening films on Thursdays, and the "Silent Sunday Nights" and "TCM Imports" blocks on Sundays.