When did the offspring form?

Answer 1

1986

This is the BEST answer with the most band members actually in the band at the time. Their name was also changed to "The Offspring" in this time period.

Below are a few "Copy and Pasted" sources of information which I grabbed from the official "The Offspring" website.

1984: Orange County high school classmates Dexter Holland and Greg Kriesel are inspired to form a band after an Irvine concert by local punk-rock heroes Social Distortion. With Holland the vocalist, Kriesel takes to the bass.

1985: School custodian Noodles joins up, allegedly for his ability to legally procure alcohol for the underage trio. The threesome practice in Kriesel's parents' house and play their first shows in Santa Cruz and San Francisco.

1986: The band, originally called Manic Subsidal, changes its name to The Offspring. They press up 1,000 copies of the debut vinyl single, "I'll Be Waiting" b/w "Blackball," on their own Black Label. The band pioneers its DIY method by glueing the sleeves together at Kriesel's house.

Sixteen-year-old Ron Welty becomes the fourth member of The Offspring after the original drummer leaves to devote more time to school.

1989: Band signs to independent label Nemesis/Cargo. With punk producer Thom Wilson (T.S.O.L., The Vandals and Dead Kennedys), they release The Offspring, their debut album, which sells 3,000 vinyl copies.

Source: http://www.offspring.com/cgi-bin/WebObjects/Offspring.woa/wa/history