And this, says media reporter Bill Carter, was the right time.
"Jay told me that really the difference with this was he went along with it," said Carter, a New York Times reporter who wrote "The War for Late Night: When Leno Went Early and Television Went Crazy" -- a book that chronicles the last time Leno left "Tonight."
"He agrees with this. He's on board with this."
This has happened before
Leno first exited "Tonight" in 2009 after 17 years as host, passing the torch to Conan O'Brien, who was then the host of "Late Night."
Leno was moved to prime time with his own program, "The Jay Leno Show," that fall.
But when that brought dismal ratings, NBC decided to put Leno back in charge of "Tonight" at the start of 2010, leaving O'Brien without a job.
Despite his short stint on "Tonight," O'Brien wished Fallon well.
"I want to congratulate Jimmy. That is a really fun gig. You laugh, but it really is," O'Brien said, trying to reassure the audience he wasn't being sarcastic. "Jimmy is the perfect guy to do it. He's going to do a fantastic job."
After getting the boot from "Tonight," the flame-haired comedian eventually moved to TBS to host his own show, "Conan," in the 11 p.m. hour, but the entire scenario generated ill will toward Leno and NBC. (TBS shares a parent company with CNN.)
Yet as the years went on, Leno has proved to be resilient.
As NBC's prime-time ratings suffered, Leno's "Tonight Show" was still able to rise above the rest in its time slot. At the end of March, "The Tonight Show" hit a seven-week high in total viewers, with 3.52 million watching.
However, NBC was said to be concerned about losing younger viewers to ABC's Jimmy Kimmel, whose "Jimmy Kimmel Live" was moved up to compete with Leno and David Letterman's "Late Show" at the beginning of 2013.
"The more time Jimmy Kimmel is in that slot, the more the young audience goes that way, the harder it is for (Fallon) to keep that audience," one source familiar with the network's thought process told The Hollywood Reporter in March.
Changing states of comedy
With the change in hosts comes a change in locales.
According to a statement from NBC, "As part of the transition, 'The Tonight Show' will be returning to its original home in 30 Rock in New York" from Leno's base of Los Angeles.
New York Gov. Andrew Cuomo praised the move, saying in a statement "on behalf of all New Yorkers" that he's "pleased to welcome 'The Tonight Show' back to its first home."
When it began in 1954, the "original 'Tonight Show' ushered in the modern era of television," Cuomo continued. "It is only fitting that as 'The Tonight Show' returns to our state, it will be headlined by New York's own native son and resident, Jimmy Fallon."
Out with the old
At 62 years old, Leno represents a more traditional form of hosting, as he's known for his "Las Vegas-style comedy," said The New York Times.
Fallon, 38, regularly incorporates the Web and social media into his act, offering "a more contemporary and varied brand of entertainment," the Times said.
This changing of the guard is one of the most closely watched exercises in pop culture, especially as it takes place at one of TV's mainstay productions.
Even with its decline in ratings over the years, it remains a solid profit center for NBC, making between $25 million and $40 million for the network, according to The New York Times.
Although it's been on the air for almost 60 years, "The Tonight Show" has had just a handful of regular hosts: Steve Allen, Jack Paar, Johnny Carson, Leno and O'Brien.