NBC, trying to regain strength in time periods it once dominated, will shake up its lead-off hours Thursday and Saturday, moving “Out All Night” to Thursday and placing “Rhythm & Blues” on hiatus, as expected (Daily Variety, Oct. 22).As part of the shift, the network will move “A Different World” back to its old 8:30 p.m. slot Thursday behind “Night”– sparing it a continued drubbing at the hands of “The Simpsons”– and bring back Norman Lear’s “The Powers That Be” at 8:30 Saturdays, hoping to provide a more compatible lead-in for “Empty Nest.” “Here and Now,” with Malcolm-Jamal Warner, continues at 8 p.m. Saturdays. The changes start during November sweeps, with Columbia Pictures TV’s politically themed “Powers That Be” kicking off with back-to-back episodes Nov. 7. That show takes its regular slot behind “Here and Now” the following week, while “Out All Night” goes to Thursday starting Nov. 19. “Blues,” from Twentieth TV, continues in production but has its last scheduled airing next week. NBC will fill the breach with a special “Fresh Prince of Bel-Air” and one-hour “Different World.” Both “Here and Now” and “Out All Night” come from the web’s in-house production wing, NBC Prods., and have drawn disappointing numbers Saturday, averaging 15 and 16 shares, respectively, since premiering Sept. 19. NBC is clearly hoping that “Night” can hold its own against “The Simpsons” and allow “World” to reassert itself opposite Fox’s first-year series “Martin,” which has topped “Blues” in their last three head-to-head airings. “Powers That Be” did fairly well last season in the same Saturday slot.