Time is a big deal in On the Road. As it ticks away, characters feel an impending sense of franticness, a fear of death, and a need to move and beat time. "Knowing time" is tied up in the word "beat," in the sense of music and keeping the time with a beat. It becomes a godly thing to "know time," and Dean pursues it as his highest goal.
Dean identifies musicians as God-like for knowing time. In doing so, he establishes his own limitations since, as a non-musician, he can never himself truly know time. Dean’s journey is then imbued with an overall sense of futility.