Yes, I know Johnny Cash performed "At Folsom Prison" in 1968... it does take time for Matt to get through the system from arrest to entering the prison.
TRANSCRIPTION COURTESY OF JOSEPH HOUK - (CW, as they travel under a freeway to the Sacramento Airport) "You know, when you said that you wanted to go back to 1967 and catch a legendary concert, I was thinking you were gonna go see the Grateful Dead, or CCR, or The Who, or maybe Jefferson Airplane..." (CW, driving with a tie-dye shirt and headband) "...not Johnny Cash at Folsom FUCKING PRISON!!!" (MG) "Hey. That was a legendary show! So what if I went and robbed a bank so I could see it in person!"