Gerald Joseph Mulligan (April 6, 1927 - January 20, 1996) was an American jazz saxophonist, clarinetist, composer and arranger. Though Mulligan is primarily known as one of the leading jazz baritone saxophonists - playing the instrument with a light and airy tone in the era of cool jazz - he was also a significant arranger, working with Claude Thornhill, Miles Davis, Stan Kenton, and others. Mulligan's pianoless quartet of the early 1950s with trumpeter Chet Baker is still regarded as one of the best cool jazz groups. Mulligan was also a skilled pianist and played several other reed instruments.

While arranging for Kenton, Mulligan began performing on off-nights at The Haig, a small jazz club on Wilshire Boulevard at Kenmore Street. During the Monday night jam sessions, a young trumpeter named Chet Baker began sitting in with Mulligan. Mulligan and Baker began recording together, although they were unsatisfied with the results. Around that time, vibraphonist Red Norvo's trio began headlining at The Haig, thus leaving no need to keep the grand piano that had been brought in for Erroll Garner's stay at the club. Faced with a dilemma of what to do for a rhythm section, Mulligan decided to build on earlier experiments and perform as a pianoless quartet with Baker on trumpet, Bob Whitlock on bass and Chico Hamilton on drums (later Mulligan himself would occasionally double on piano). These early live dates were recorded by Dick Bock on a portable reel-to-reel tape deck. Bock along with Roy Harte would soon after, start the Pacific Jazz label and release Mulligan's records. Mulligan's first recording sessions in Los Angeles were produced by Bock for Pacific Jazz. These three informal sessions took place in June, July, and August 1952 at the Hollywood Hills cottage of recording engineer Phil Turetsky. At these sessions, Mulligan, Chet Baker, and others recorded the material that was released as Pacific Jazz PJ LP-1 and later on PJ-8. Baker's melodic style fit well with Mulligan's, leading them to create improvised contrapuntal textures free from the rigid confines of a piano-enforced chordal structure. While novel at the time in sound and style, this ethos of contrapuntal group improvisation hearkened back to the formative days of jazz. Despite their very different backgrounds - Mulligan, a classically trained New Yorker, and Baker, from Oklahoma and a much more instinctive player - they had an almost psychic rapport and Mulligan later remarked that, "I had never experienced anything like that before and not really since." Their dates at the Haig became sell-outs and the recordings they made in the fall of 1952 became major sellers that led to significant acclaim for Mulligan and Baker. The recordings included singles such as "Motel" (1953) labelled as 'The Gerry Mulligan Quartet Featuring Chet Baker'. This fortuitous collaboration came to an abrupt end with Mulligan's arrest on narcotics charges in mid-1953 leading to six months at Sheriff's Honor Farm. Both Mulligan and Baker had, like many of their peers, become heroin addicts. However, while Mulligan was in prison, Baker transformed his lyrical trumpet style, gentle tenor voice and matinee-idol looks into independent stardom. Thus when upon his release Mulligan attempted to rehire Baker, the trumpeter declined the offer for financial reasons. They did briefly reunite at the 1955 Newport Jazz Festival and would occasionally get together for performances and recordings up through a 1974 performance at Carnegie Hall. But in later years their relationship became strained as Mulligan, with considerable effort, would manage to kick his habit, while Baker's addiction bedevilled him professionally and personally almost constantly until his death in 1988. CANNOTANSWER

Using a quote from the above article, answer the following question: When did they form the quartet?

These three informal sessions took place in June, July, and August 1952