Six nights of the week, primetime begins at 7 or 8 p.m. On Saturday, it starts at 11:30.Credit the latenight time shift to Michaels, who created comedy-variety show “Saturday Night Live” in 1975, with George Carlin stepping in as the first host. From the Killer Bees to Wayne’s World, from Operaman to Mango, “SNL” has gone through its creative ups and downs but remains a cultural force. Michaels has helped shape the careers of an army of “SNL” vets, including John Belushi, Adam Sandler, Chris Rock and Will Ferrell. The Canadian-born producer arrived in Gotham after working as a writer on “Laugh In,” helping NBC produce an original sketch-comedy program together in place of “Tonight Show” reruns. Thirty years later, no other network has ever won that timeslot.