(E News) - It's a new day for Green Day.
On Sunday, the Grammy-winning rockers performed at the Fox Theater in Ponoma, Calif., to a sold-out crowd. The gig, which kicked off the group's U.S. tour, marked the first of four "warm-up" shows before the band hits up larger stadiums, beginning with the Allstate Arena in Rosemont, Ill., on March 28.
Armstrong himself appeared to be back in tip-top shape: Per Rolling Stone, he repeatedly screamed "Let's go f--king crazy!" throughout the show.
It's a marked change from the band's notorious performance at the iHeartRadio festival in Vegas last September, during which Armstrong had an onstage meltdown that included a cuss-filled rant and a guitar-smashing rampage. Two days later, the frontman checked into rehab for substance-abuse issues.
In a recent interview with Rolling Stone, Armstrong opened up about his drug-fueled days, telling the mag, "I couldn't predict where I was going to end up at the end of the night."
He also recalled, "I'd wake up in a strange house on a couch. I wouldn't remember how. It was a complete blackout."
After seeking treatment, Armstrong took to Instagram in December to thanks his fans for their support.
"Believe me, it hasn't gone unnoticed and I'm eternally grateful to have such an amazing set of friends and family," he wrote. "I'm getting better everyday."