Green Day may be busy promoting their upcoming album Father of All..., but Billie Joe Armstrong turned to the past during a recent interview where he opened up about a song inspired by tragedy.

The frontman revealed that his father Andrew Armstrong passed away when he was 10, recalling that he told his mom "Wake me up when September ends" after his dad's death. When asked if he wrote down the phrase or if the words just stayed with him, Billie Joe said “I think it’s something that just stayed with me; the month of September being that anniversary that always is just, I don’t know, kind of a bummer. But it’s weird: when things happen like that when you’re that young, it’s almost like life starts at year zero, or something like that.”

The American Idiot single still brings back memories for Billie Joe when he performs it, too. But they're not all negative “I think about him every day, really. I kinda avoided writing about him for many years, and then finally having a breakthrough like that felt good. It wasn’t like a negative emotion so much, but it was just kind of like honoring him.”

"Wake Me Up When September Ends" is sure to be on Green Day's set list when they embark on the Hella Mega Tour with Weezer and Fall Out Boy next summer. Check out those tour dates here and revisit the somber song below.