The Sydney-based band 5 Seconds of Summer has been together since 2011 and, more importantly, drummer Ashton Irwin joined the band exactly four years ago tomorrow, Dec. 3, completing the lineup.

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Last year the Aussies celebrated with a playlist of videos from over the years on YouTube.

Irwin and his bandmates Luke Hemmings, Calum Hood and Michael Clifford recently stopped by James Corden's The Late Late Show to promote their sophomore album Sounds Good Feels Good.

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While chatting with Corden the band members reminisced about how they became a band. They have late night Facebook messaging to thank.

"We booked a gig and we said to ourselves, 'We probably need a drummer,'" Hood recalled of his interaction with Hemmings and Clifford before Irwin joined the band.

"Michael messaged me at 2 a.m.: 'What you doin'?'" Irwin recalled, adding his response and everything fell into place since then.

Corden thinks their late night Facebook messaging story is "the best" despite Hemmings calling it lame.

Corden would be right. These four have accomplished so much in such a short time, including the release of two full-length studio albums, a live album, a lot of touring and numerous awards--the list goes on.

With all of this in mind, Irwin got nostalgic on Twitter early Wednesday with the band's anniversary coming up tomorrow.

"Tomorrow is 4 years since I joined the band at that pub back in Sydney..." he dished, adding, "Never thought all this would happen."

It's certainly amazing what could come of a late night Facebook chat.