Jay Leno and Jimmy Fallon backstage at the 70th annual Golden Globe Awards in Beverly Hills, Calif., on Jan. 13. (© Lucy Nicholson / Reuters)

For the second time in about four years, Jay Leno is stepping down from NBC’s iconic late-night franchise “The Tonight Show.” This time, he’ll exit in spring 2014 to make way for “Late Night” star Jimmy Fallon.

Fallon will take over sometime after that, the network announced Wednesday, confirming the industry’s worst-kept secret in recent history.

NBCUniversal chief executive Steve Burke explained that the timing is intended to mesh with NBC’s broadcast of the Winter Olympic Games from Sochi, Russia, which we swear is the truth and not a gag from an “SNL” skit.

“Saturday Night Live” impresario Lorne Michaels will become executive producer; Debbie Vickers, who has produced the show for the past two decades, will exit along with Leno. And the show will return to its original home at 30 Rock in New York, where it was based until Johnny Carson, “Tonight’s” longest-running host at 30 years, moved it to Burbank in 1972.

“We’re thrilled ‘The Tonight Show’ is returning home to New York City, and it’s the perfect symbol of incredible comeback we’ve worked to create in our city’s film and television industry,” Mayor Michael R. Bloomberg weighed in Wednesday, followed by a bunch of political “not since the invention of television has so much production been based in our city,” blah, blah, blah — and finally running out of gas with, “and we couldn’t be happier that one of New York’s own is bringing the show back to where it started — and where it belongs.”

There’s no news on Fallon’s “Late Night” replacement at 12:35 a.m. NBC said coyly in its announcement that “programming plans” for the time period are in development and will be announced soon. Under consideration is the return of “The Tonight Show” to its 90-minute format. (“The Tonight Show,” which debuted in 1954, with Steve Allen as host, was cut down to one hour during Carson’s long run.)

“We are purposefully making this change when Jay is number one, just as Jay replaced Johnny Carson when he was number one,” Burke said.

There’s one big difference: Carson shocked NBC suits in 1991 when he announced his retirement at an affiliate conference in New York. That followed news reports that NBC was concerned that Carson (who was in his mid-60s) was losing younger viewers, and that NBC had guaranteed Leno the gig when Carson retired. Leno took over the show in 1992.

Leno, 62, on the other hand, is being told when to step down — again. His contract expires next year.

The other time Leno was informed that he was stepping down as “Tonight” host, it was to make way for then-“Late Night” host Conan O’Brien. NBC announced in fall 2004 that the network negotiated a contract with Conan that promised him he’d replace Leno on “Tonight” in June 2009.

In Wednesday’s announcement, NBC made no mention of Conan by name.

In May 2009, Conan interrupted Leno’s run for seven months, as NBC parked Leno at 10 p.m. weeknights, where he provided Conan with lousy lead-in ratings. Leno, you’ll recall, regained the “Tonight Show” keys after NBC decided to push the Conan-hosted show’s start time to 12:05 a.m. to squeeze Leno back into late night in some newly named half-hour late-night program.

Conan did not sign, however, saying he’d rather walk than see “Tonight” moved to 12:05 a.m. And he did.

 Leno is not being moved out because he’s failing in the ratings. This season, “Tonight” is consistently beating ABC and CBS time-slot rivals among the 18- to 49-year-old viewers; Leno is also first among viewers of all ages, regularly attracting an average of 3.5 million.

But Leno is in his 60s. When ABC moved Jimmy Kimmel, 45, to 11:35 p.m. in January, the media began speculating that Kimmel would scoop up all the young viewers in the time slot before Leno’s heir apparent, Fallon, 38, eventually moved into the time period.

Since his debut in the earlier time slot, Kimmel has achieved a slight lead (332,000, on average) over Leno (319,000) among 18- to 34-year-old viewers.

Leno is Kimmel’s favorite punching bag. Kimmel tweeted Wednesday: “congratulations to my dear, sweet @jimmyfallon — a formidable rival and an incredible lover.”

Elsewhere: “How many of you folks earlier today saw the white smoke coming out of the chimney at NBC? Anybody see that?” David Letterman — the guy whom Leno beat out for the “Tonight” gig back when Carson retired — said at the top of his CBS late-night show hours after NBC’s announcement.

“I got a call from my mom today. She says, ‘Well, David, I see you didn’t get ‘The Tonight Show’ again,’ ” Letterman continued. Also: “Good luck to Jay. I know he’ll be out on the road, getting it done and taking care of business and congratulations on a nice, long run there at ‘The Tonight Show,’ if in fact you’re not coming back.”

Interestingly, Fallon — because his humor is broader and sweeter than Conan’s — might be better suited to take over for Leno than was Conan because of his greater appeal to older viewers. When Conan took over “Tonight,” he’d lost a lot of his edge over CBS competitor Craig Ferguson among total viewers.

Since Fallon’s arrival, “Late Night” is once again more consistently beating Ferguson in total viewers.

Leno did not go gently into that good night. In the days leading up to Wednesday’s announcement, he savaged NBC in his monologues. But this week, signaling that an announcement was imminent, he and Fallon teamed for a duet, which became  a YouTube sensation, of course.

“Hey kid, how you holding up?” Leno was seen asking Fallon over the phone, just after the camera showed Leno sadly exiting the stage, and Fallon forlornly looking out his office window.

“Okay, I guess. You?” Fallon replied.

“Yeah, I’ll live. I’ve been through this before,” Leno sighed. “Gotta admit, I’m getting a little sick of all of this.”

Fallon looked troubled: “Jay, can I ask you something? We’re still friends, right?”

“Yeah, of course we’re still friends,” Leno assured him.

“That’s good,” Fallon said, relieved.

Cue duet of the “West Side Story” tune “Tonight,” with lyrics rewritten as befitted the occasion.

TV critics hated it — real schmaltz, they scoffed, as they nicked the hip Fallon for having caved to pressure to do the video. Hollywood Reporter’s Tim Goodman, for instance,  snarked: “The video isn’t funny. It’s too long. Doesn’t have an ounce of believability and plays like a clip from a Hallmark movie about lovers that’s airing sometime soon on Bravo. And it makes Fallon look like simpering suck-up who sold out because he was probably told to.”

Then came word that it was Fallon’s idea. Oops.

To read previous columns by Lisa de Moraes, go to washingtonpost.com/