Davis had met Los Angeles Rams coach Sid Gillman in Atlantic City at a coaching clinic; the NFL coach had been impressed that Davis had sat in the front row, taken copious notes, and had asked many questions afterwards. Gillman was fired after the 1959 season, but was quickly hired in by the Los Angeles Chargers of the startup American Football League (AFL) for their debut 1960 season. He hired Davis as backfield coach on a coaching staff which included future hall of famer Chuck Noll as well as future AFL head coach and NFL general manager Jack Faulkner. Gillman later stated that he hired Davis for his success both as a coach and as a recruiter, and because "Al had that knack of telling people what they wanted to hear. He was very persuasive."  The AFL's rules were crafted to encourage wide-open, high-scoring football. In later years, much to Gillman's anger, Davis hinted that he had designed the Chargers's offense, or at least deserved partial credit. The team initially proved successful, winning the AFL Western Division in 1960 and 1961, though losing each time in the AFL Championship Game to the Houston Oilers. Due to financial losses sustained by drawing small crowds to the huge Los Angeles Coliseum, the team moved to San Diego in 1961. In 1962, however, the team won only four of fourteen games.  One player whom Davis recommended to the Chargers, and then secured, was wide receiver Lance Alworth of Arkansas, who was a first round selection of NFL San Francisco 49ers in the 1962 NFL Draft. Unwilling to give the 49ers a chance to sign him, Davis raced onto the field at the conclusion of Alworth's final college game and signed him to a contract under the goalpost as 49ers head coach Red Hickey watched helplessly from the stands. Davis later stated, "I knew it wasn't safe to let Alworth go to the dressing room." In 1978, Davis was selected by Alworth to introduce him at his induction to the Pro Football Hall of Fame in Canton, Ohio.

Answer this question "When did Al Davis join the Chargers?" by extracting the answer from the text above.
1960 season.