Green Day's 'Dookie' Turns 30: Billie Joe Armstrong Reveals Why the Band Was 'Freaked Out' Before It Dropped (Exclusive)

Green Day celebrated a major milestone on Thursday: The band’s seminal album, Dookie, turned 30.

The album — which included hits like “Basket Case,” “When I Come Around” and an updated version of “Welcome to Paradise,” which appeared on the band’s second album, Kerplunk — marked a mainstream breakthrough for frontman-guitarist Billie Joe Armstrong, bassist Mike Dirnt and drummer Tré Cool.

Then an indie trio, Green Day cut their teeth playing shows on the Bay Area punk scene, where they found a fervid following before signing a major-label record deal.

“I didn't know, man. I was so freaked out at that point because we had taken the biggest gamble of our lives,” Armstrong, 51, recently told PEOPLE of going from indie darlings to a major-label act and recording Dookie. “We knew what we wanted to do, the kind of record we wanted to make, and we rehearsed every single day before we got into the studio. We just wanted to be as strong as possible, and we felt like we made a great record. We were really happy with it.”

Armstrong and his bandmates had hesitations, though, and weren’t sure how fans would react.

“You never know what is going to happen as far as what the public is going to think — and even our own fan base at that time was going to think,” Armstrong recalls, “because a lot of it was the controversy of us going from an indie to a major label.”

The album, of course, resonated with fans and became a hit, catapulting Green Day to rock stardom — and the Grammys (in 1995, they received four nominations and took home their first Grammy).

“It was also very exciting at the same time,” Armstrong says of their meteoric rise. “All of a sudden, we're playing Lollapalooza and Woodstock, and our shows were getting bigger. We were on MTV. That was a lot of fun. But it was a double-edged sword, a little bit.”

Last month, Green Day released their acclaimed 14th studio album, Saviors. And in May, the group will hit the road for their Saviors World Tour, on which they'll play Dookie and American Idiot (which turns 20 in September) all the way through.

All these years later, Armstrong’s punk-rock ethos remains steadfast.

“I still try to maintain that kind of spirit about what we do,” the Oakland-based singer recently told PEOPLE, “which is just being independent and free to express yourself the way that you want.”