Time magazine named Richard Stengel, a 20-year veteran of the newsweekly, as its new editor yesterday, replacing Jim Kelly, who is taking a senior position at corporate parent Time Incorporated.

Mr. Stengel, who is 51 years old, had worked at Time in several different capacities, including national and culture editor and also editor of Time’s Web site, Time.com. Most recently he was head of the National Constitution Center, a Philadelphia-based museum and nonpartisan think tank focusing on civic issues.

Mr. Stengel will assume his duties at Time Incorporated’s flagship magazine on June 15, when Mr. Kelly takes on a newly created job of managing editor of Time Incorporated, where he will work on broad issues of standards, ethics and practices.

The changing of the guard at Time comes as newsweeklies face mounting pressure to adapt their traditional business models at a time when more and more people get up-to-the-minute news from various online sources.

In announcing the appointment, John Huey, the top editorial executive at Time Incorporated, described Mr. Stengel as “a true multimedia editor” as well as someone who has “an outsider’s perspective and the insider’s appreciation and knowledge of who and what makes Time tick.”

In addition to his stint at the National Constitution Center, Mr. Stengel also has written for other publications including the New Yorker and the New York Times. He also worked as the chief speechwriter for former presidential candidate Bill Bradley and collaborated with Nelson Mandela on his autobiography “Long Walk to Freedom.”

Time Incorporated, a subsidiary of New York press and broadcasting conglomerate Time Warner Incorporated, has been going through some struggles of its own, and last year cut a number of senior executive jobs, including the president of Time magazine, Eileen Naughton, who departed as part of an overhaul of Time Incorporated’s corporate structure.