Green Day was formed in 1987 in the East Bay area of California by Billie Joe Armstrong and Mike Dirnt.

Quick Scoop

  • Year formed: 1987.
  • Place: Rodeo/East Bay, California punk scene.
  • Founding members: Billie Joe Armstrong (guitar, vocals) and Mike Dirnt (bass).
  • Early name: They originally played under the name “Sweet Children” before becoming Green Day.

So if you’re ever wondering “when was Green Day formed,” the answer is 1987—right at the heart of the late‑80s Bay Area punk wave.

TL;DR: Green Day started in 1987 in the East Bay, California, when Billie Joe Armstrong and Mike Dirnt formed a punk band that would soon take the name Green Day.

Information gathered from public forums or data available on the internet and portrayed here.