Answer by taking a quote from the following article:

No Doubt is an American ska band from Anaheim, California, that formed in 1986. Since 1994, the group has consisted of vocalist Gwen Stefani, bassist and keyboardist Tony Kanal, guitarist and keyboardist Tom Dumont, and drummer Adrian Young. Since the mid-1990s in live performances and the studio, they have been supported by keyboardist and trombonist Gabrial McNair and keyboardist and trumpeter Stephen Bradley. The ska sound of their song, "Trapped in a Box" (1992), that was featured on their first album

Eric Stefani and John Spence met at a Dairy Queen and had talked about getting a group together to play music. Eric got a keyboard and gathered some players together to practice. The practice included Eric Stefani (keyboards), Gwen Stefani (backing vocals), John Spence (lead vocals), Jerry McMahon (guitar), Chris Leal (bass), Chris Webb (drums), Gabriel Gonzalez & Alan Meade (trumpet) and Tony Meade (saxophone). They practiced in Eric's parents' garage.  Tony Kanal went to one of the band's early shows and soon joined the band as its bassist. After initially rejecting her advances, he began dating Gwen, but they kept their relationship secret for a year, feeling that it was an unspoken rule that no one in the band dates her. Paul Caseley (trombone) also joined the band in 1987. Eric Carpenter (saxophone) joined the horn section soon after.  In December 1987, Spence committed suicide several days before the band was to play a gig at The Roxy Theatre for record industry employees. No Doubt disbanded but decided to regroup after several weeks with Alan Meade taking over vocals. When Meade left the band, Gwen replaced him as lead singer, and No Doubt continued to develop a live following in California. In early 1988, Tom Dumont left Rising, a heavy metal band of which he was a member with his sister, stating that local metal bands "were into drinking, wearing Spandex" but that he wanted to focus on music. He joined No Doubt and replaced Jerry McMahon as the band's guitarist. Adrian Young replaced Chris Webb as the drummer the following year. During this time period, No Doubt played gigs at local colleges, Fender's Grand Ballroom, The Whisky, The Roxy, many shows with The Untouchables, Fishbone, and a show with the Red Hot Chili Peppers at Cal State Long Beach. Caseley left No Doubt in July 1989 for the US Navy Band.

when did they form into the band?