Mark Hoppus never wants to act his age, and neither did the 15,000 people in attendance to see Blink-182 at the sold-out Nikon at Jones Beach Theater on Saturday night.

The crowd was filled with young adults in their mid-20s seemingly trying to relive their high school days. Former frat bros in snapbacks and tank tops put their arms around each other’s shoulders as Blink’s emotional 2003 hit “I Miss You” echoed through the venue. Young women snapped videos of themselves screaming along to “All the Small Things,” using apps and technology that was unimaginable when that song came out 15 years ago. For a few hours, thousands of people tacitly agreed to ignore the incessant lightning, forget about adult responsibility and to party like it’s 1999.

The 24-song setlist piled on the hits, clearly giving the crowd of longtime fans what it wanted. Technically, the band was promoting its seventh studio album, “California,” so it played just enough new songs to remind the crowd that this is not a reunion tour.

In fact, the California Summer Tour was far from a reunion — it’s the band’s first tour with its new guitar player, Matt Skiba of Alkaline Trio. The band’s 2016 release was its first without Tom Delonge, the band’s original guitar player, co-lead vocalist and co-songwriter, along with bassist Mark Hoppus.

The show certainly went on without Tom, albeit slightly differently. Musically, Skiba was a fine replacement. He took the lead when he needed to, sang harmonies when appropriate, but his energy was not the same. In their prime, Mark and Tom were known for their onstage chemistry. The two had been friends since they were teenagers, and their sense of humor and public personas hardly matured even when the men were well into their 20s and 30s. Some old gags remained in the setlist, but for the most part, the Mark and Tom show turned into just Mark.

The 44-year-old, who is the only founding member that remains, spent a majority of the show skipping and trotting across the stage as if he couldn’t decide where he really wanted to be. His energy was like that of a 13-year-old boy and was aided by small explosions, light shows and fire that also could have been orchestrated by a teenager

The added spectacles, while fun, seemed like a distraction to the fact that these 40+-year-old men where singing about being 23 and 17, attending Warped Tour and taking girls out on first dates. The trio was slightly too old to be singing about such topics, even when the songs were first released, so it sounds even more awkward now. But because of the killer combination of the ocean breeze, cold beers and pure nostalgia, no one seemed to mind.

Blink-182 provided the audience with exactly the show it wanted last night — an hour and a half of mindless immaturity. Fifteen thousand people were connected by the shared experience of these songs following them through adolescence. And what has changed in the last 15 years since Blink-182 first broke out on the scene? Most of the audience was probably not legal in 1999, and most of them probably didn’t hold steady 9 to 5 jobs, but really, those things don’t seem so big.

Last night, Blink-182 reminded us that the important things are timeless. Music is still fun, friends are still silly and summertime is still special. They reminded us that being young is a mindset. Last night, thanks to Blink-182, we were all young again, if only for a moment.