Earlier this year, Willie Nelson was nominated for the Rock and Roll Hall of Fame, having already been inducted into the Country Music Hall of Fame in 1993. Both a living legend and a relatable everyman, Willie turns 90 years old today, and it’s tempting to mark the occasion with yet another retrospective. But the beats and tribulations of his life have already been well covered in a lifetime of magazine profiles and biographies. And anyway, judging by the small library of memoirs he has released, nobody can indulge such retrospection better than the man himself. Rather, reflecting on his journey today, I’m struck by the enduring relevance of a single song: “Funny How Time Slips Away.”

What about this deceptively simple composition—a fairly basic chord structure, three unadorned verses, and no chorus to speak of—makes it so evocative and enduring, so endlessly adaptable across the divides of genre and generation? What does “Funny” reveal not only about the artistry of Willie Nelson, but also about the culture that venerates him?

Since its first recording more than 60 years ago, the song has continued to evolve. After early renditions by Billy Walker, Jimmy Elledge, and Nelson himself in the early 1960s, the song quickly transcended its country roots in the Nashville Sound. An impressive cohort of artists subsequently reinterpreted the song in diverse styles: the too-cool croon of Elvis Presley; the silky groove of Al Green; the easy-listening of Perry Como; the soulful R&B of Dorothy Moore; the Beale Street blues of B. B. King. To such esteemed company, one might also add Stevie Wonder, Norah Jones, Lyle Lovett, The Supremes, The Spinners, Leon Bridges, Tennessee Ernie Ford, and many, many others.

Meanwhile, Willie has offered his own repeated reimaginings. He has performed “Funny” as a lovelorn serenade, a lonesome jazz ditty, an orchestral ballad, a brass-band tune, a blues duet, and more. “Funny How Time Slips Away” has no authoritative, canonical version. This creates a strikingly open field of interpretive possibilities, each of which changes the emotional impact and very meaning of the song.

In essence, “Funny” depicts a jaded narrator running into an old flame. The three verses comprise only one side of the ensuing conversation. With poetic economy, Nelson spins a tale that blends heartbroken earnestness with scathing self-deprecation, sincere nostalgia with tragic pettiness. Decades before Lionel Richie and Adele would execute the same rhetorical maneuver, Nelson begins with an ambiguous greeting: “Well, hello there.” From this first line, the song coaxes listeners in and immediately knocks them off balance. Are we meant to identify with the narrator? Are we the addressee? Or are we eavesdropping on a conversation?

All of this remains unspecified, and so, too, do our sympathies. The narrator dons an air of blasé detachment, as if he had almost, but not quite, forgotten about the former love. Listeners recognize this as a sad pretense, of course, and that tension gives the song its edge. Each verse casts new light (and new shadows) on the characters’ relationship, yet in a way that always remains between the lines. The ruse gradually unravels, revealing a core to the song that is heartbroken and embittered. The narrator’s words are riddled with artifice and contradiction throughout. Take the title and refrain, for instance: The use of funny is clearly euphemistic rather than literal, but a euphemism for what exactly? Depending on the performer, funny can alternately imply any number of reactions to time’s passage: fascination or frustration, consolation or disconsolation, regret or gratitude, wistfulness or outrage.

Or consider the last line: “But remember what I tell you / That in time you’re gonna pay.” Is this a credible threat? A pathetic cry of impotent rage? An ice-breaking joke meant to acknowledge the narrator’s previous, since-worked-through anger? (Indeed, many versions place this line in the past tense—“But remember what I told you”—which clouds the exegetical waters even further.) Semantic elasticity is the song’s secret weapon. Its lyrics are concrete enough to feel real, but hazy enough to justify numerous readings. “Funny” endures precisely because of its capacity to nourish ever-changing emotional landscapes.

Of the countless renditions, my personal favorite is Nelson’s stripped-down live recording from a gathering of country songwriters in 1997 (later released on Ralph Emery’s Country Legends Series Volume 1). It is a softer, more weather-beaten performance, inflected with Nelson’s inimitable jazzy licks and bold chromatic transitions. Embracing his elder-statesman role in American music, Nelson’s performance lays bare the sting of retrospection and transcends the faux detachment of the song’s narrator. In the hands of late-stage artists, one gets a visceral sense of time escaping, adding a meta-textual gravity to a song that is, fundamentally, about the passage of time. Glen Campbell and Dr. John both recorded the song in their twilight years; both recordings were released on their final albums. With age, the titular sentiment evokes something far bigger than lost love—namely, that tangled sense of regret, satisfaction, and melancholy that accompanies getting older.

Like the song, Nelson wears many faces: cowboy and hippie, patriot and renegade, churchgoer and gambler. He is America’s grandpa and the only person to ever out-smoke Snoop Dogg. He is a songwriter of stubborn originality as well as an earnest interpreter of the Great American Songbook. Perhaps nothing distills his genius nor encapsulates his capacious cultural resonance better than “Funny How Time Slips Away.” The song is simultaneously a reliable standard and a musical shape-shifter, just like its songwriter. In short, we love “Funny” for the same reason we love Willie himself: It contains our multitudes and welcomes our contradictions. The brilliance of both lies in their ability to project whatever one most needs to receive. In the song, each can hear their own story. In Willie, each can see their own hero.

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