Green’s Dictionary of Slang

1. (N.Z. prison) time spent in solitary confinement.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 61/2: down time n. time spent in the solitary confinement punishment cell.

2. relaxation, time spent in some form of ‘off duty’.

1991		B. McCarthy Vice Cop 1240: They were all off-duty now [...] Everybody needed a break.
2023		A. Nette Orphan Road 14: ‘Don’t worry, Gary, the coke is for down time only [...] I’m always clean when I work’.