For the second time in its young life, “Rock Center with Brian Williams” is moving on the NBC schedule. Starting next Wednesday, March 7, the show will air at 10pmET/PT. “Rock Center” had been on at 9pmET since earlier this month when it moved from Monday nights. The move is temporary, with plans to return to 9pm April 11. “Rock Center” has struggled in the ratings posting an all-time low last week with just 2.6 million viewers tuning in. Williams averages more than three times that on his “Nightly News,” during a time of day when there are far fewer homes watching television.