Green Day is a team.
Green Day is an American punk rock band formed in 1986 by lead vocalist and guitarist Billie Joe Armstrong and bassist Mike Dirnt . For much of the group 's career , the band has been a trio with drummer Tré Cool , who replaced former drummer John Kiffmeyer in 1990 prior to the recording of the band 's second studio album , Kerplunk ( 1991 ) .