The big developments in late-night television are not all happening on NBC this week. Adult Swim, the network that is, in many ways, the new force in late night, has some significant news, too: It is expanding again.

Though its programming usually draws far less media attention than, say, the changing of the guard on NBC’s “Tonight” show, Adult Swim has amassed enviable viewership numbers: Among the audience groups many advertisers want most to reach, Adult Swim beats just about everything else in late night.

On Tuesday, the network will announce that it is adding another hour of programming to its schedule, moving further backward into prime time. Starting March 31, Adult Swim — a mix of animated and live-action shows, replete with the kind of irreverent humor that has been the stock-in-trade of late-night television for half a century — will offer programming from 8 p.m. to 6 a.m. every day. It is claiming that hour from the Cartoon Network, which occupies the same channel space in the daytime hours and is also owned by Turner Broadcasting.

In explaining the move, Stuart Snyder, the president of Animation, Young Adults and Kids Media for Turner Broadcasting, said the time was right for the additional hour “coming off a record-setting ratings year in 2013.” Not to mention the “increasing demand we are receiving from advertisers,” he said.