It's an indication of how quickly life moves for the lads of One Direction that their idea of ancient history appears to be 2012.
That's when Harry Styles — the youngest (and arguably dreamiest) member of this British boy band — was 18, an age he and his mates recall on their new album as though the memory were nearly lost to the mists of time.
"I have loved you since we were 18," they sing over strummed acoustic guitar in "18," as full of yearning as James Garner at the end of "The Notebook." "I want a love like you made me feel when we were 18."
The exaggerated emotion of youth? Well, duh — that's the business One Direction is in. Here's the thing, though: Go back and listen to Styles at that age — on the band's second album, "Take Me Home" — and two years really does seem like an eternity.
There's no sense on "Four," released this week, of the excitable, fresh-faced kids first assembled by Simon Cowell on the British edition of "The X Factor." And there's only a trace of the rowdy rock crew heard on last year's "Midnight Memories," the success of which helped drive ticket sales for One Direction's recent stadium tour.
Instead, the band's fourth record reveals a group of soft-pop smoothies, now aged 20 to 22, pulling from the same hip reference points as your average Coachella act: Fleetwood Mac, the Beach Boys, David Bowie. They're growing up not by going wild but — get this — by relaxing. And the result is their best work yet.
That connection to "Midnight Memories," by the way, comes right at the top of "Four" in the form of "Steal My Girl," which (in a sly nod to the earlier album's Who-mimicking "Best Song Ever") begins as a virtual replica of "Faithfully" by Journey. Once it kicks in, though, the song's slow-motion beat provides a swagger that feels new for One Direction, which even at its naughtiest would never have been mistaken for a threat.
"Everybody wanna steal my girl / Everybody wanna take her heart away," they sing. "Couple billion in the whole wide world / Find another one 'cause she belongs to me."
They're similarly sure of themselves in "Fireproof," in which they insist, "Nobody knows you, baby, the way I do," over a hypnotic groove that echoes Fleetwood Mac's "Gypsy." (Other songs openly crib riffs from Tears for Fears and the French band Phoenix, yet another sign of the group's confidence.)
But even when thoughts of romance turn darker — as in "Where Do Broken Hearts Go" and "Fool's Gold," about knowingly falling for a lover who "turned it on for everyone you met" — the music stays lustrous, even sensual, with shimmering guitars and unhurried beats. "Stockholm Syndrome" sets a story about being taken hostage against sleek disco licks that make the scenario, one surely imagined in the oodles of One Direction fan fiction found online, sound like a kinky good time.
In "Night Changes," they're worrying about aging: "We're only getting older, baby, and I've been thinking about it lately / Does it ever drive you crazy just how fast the night changes?" Again, though, the steady tempo and sleepy vocals, closely miked to catch every slur and crack, suggest that growing up is just another term for chilling out.
That's hardly a realization in sync with the demand for a boy band to stay forever young. But assuming they don't first split for the inevitable solo careers to come, it might be what keeps One Direction together.
At least for two more long years.