Green’s Dictionary of Slang

(Aus.) a twelve-month prison sentence.

1895		Crowe Sydney Sl. Dict. 4: All the Year Round, twelve months in prison.
1941		Baker Popular Dict. Aus. Sl.
1945		Baker Aus. Lang. 141: Here is a brief glossary of jail sentences: lag, three months. snooze, three months [...] rest, twelve months. all the year round, twelve months.