How long did Metallica's recording sessions for The Black Album last?

Metallica’s recording sessions for The Black Album lasted about eight months.

The band recorded from October 1990 through June 1991. The main work took place at One on One Recording Studios in Los Angeles, with about a week at Little Mountain Sound Studios in Vancouver and later overdubbing and mixing at A&M Studios in Hollywood.

The extended schedule reflected the band’s perfectionism and the demanding production process. Producer Bob Rock encouraged Metallica to record collaboratively and to repeat performances until the desired feel was captured. Selecting and editing the best parts from numerous takes also consumed substantial time.

The eight-month figure refers to the recording process, not the album’s later promotion. Metallica then toured extensively, and the documentary A Year and a Half in the Life of Metallica followed both the making of the album and the tour that supported it.