Twenty years later, Ben Gibbard is reliving his banner year.

In 2003, the singer’s main band, Death Cab for Cutie, had just released its biggest breakthrough yet: Transatlanticism, an album that quickly came to represent all the big emotions and soft melodics of the early aughts indie rock scene. Key spots in the hottest TV show of the day — “The O.C.” — helped Death Cab reach even further into the suburbs. Also that year, Gibbard’s side project, The Postal Service, dropped its first and only album: Give Up, a collection of instantly-catchy, jittery, electronic dance songs created with producer Jimmy Tamborello. Both records were huge. Fans learned every anguished word, memorized every swelling guitar lick. And they helped establish Gibbard as one of the most recognizable voices in indie. Death Cab continued to grow, but The Postal Service disappeared — one became a rock institution, the other a beloved cult favorite.

So when the bandleader announced a full tour playing both albums in full, the collective ears of indie rock fans now in their 30’s and 40’s perked up from their home office laptops offices across the country — every date on the 30-show tour sold out.

In Philadelphia’s Mann Center on September 21, the excitement to tap back into the emotional peaks of high school or college was palpable. As a Death Cab show is a far more common occurrence, the band took the stage first. From the first flutters of Transatlanticism’s opener, “The New Year,” fans gasped and uttered “Oh… my god.” People rocked back and forth. They cried. The bridge back to youth was instant. Or, as one woman near the front put it, “It’s like muscle memory. I know every word to every song.”

The band, of course, has changed in the past 20 years. Ben Gibbard is a seasoned rock star now — and he bounded across the stage more energetically than he did in 2003. He didn’t engage too much; the songs spoke volumes, and offered some reflection on growing up. It’s rare that a band, even from the open-hearted aughts, has written about the big insecurities of being a teenager so precisely — so when Gibbard sang, “We looked like giants, in the back of my gray subcompact, fumbling to make contact,” it felt like 14,000 fans, many here with partners, and with kids at home, were transported back to some truly formative memories.

After Transatlanticism’s hushed closer, “A Lack of Color,” and a sharp, 15-minute set break, Gibbard’s second act was up. He’d switched from all-black to all-white; an apt clothing swap, as Give Up has always been a lighter, more playful foil to Transatlanticism’s deep, cinematic sweep. Those heavy emotions already purged, the crowd was ready to bop.

Singer Jenny Lewis, one of a few guest singers on Give Up, joined the band, allowing for a more interactive energy as the two traded lines on duets like “Nothing Better.” The act’s biggest hit, “Such Great Heights,” was booming, backed by massive strobe lights and Tamborello’s bass-heavy programmed beat. But the nostalgia cut just as deep. On “Sleeping In,” a glitchy song detailing dreams of global warming, Lewis and Gibbard sang “Don’t wake me, I plan on sleeping in — now we can swim in any day in November.” For the crowd, those once-far-off climate fears are here; and the urge to sleep in isn’t to miss class — it’s to avoid the crush of another workday.

The show presented two bands tied tightly to a moment in time; the tour’s drawn in thousands of people longing to touch that simplicity again, even if life felt so complex at the time. In the penultimate song from Give Up, “Brand New Colony,” the whole crowd sang along to a chorus whose meaning they’d only internalized in the 20 years since it came out: “Everything will change.”

The music sounded the same as it did back then, and the audience’s collective relief felt like one massive exhale. They sang along to a few last songs, then flooded out into the parking lot to return to their lives, where nothing was the same.