ANZ3 and ANZ4 are on reverse timezone, as of last night.
So 8PM on ANZ1 and ANZ2 (Which is running AEST, or +10GMT), is actually 8AM on ANZ3 and ANZ4.
This means all the lads getting home in the afternoon can stay up late and play DayZ and not NightZ. It also makes it easier to shut down these servers during off-peak times as most players won't want to play on it during the dark (which is early morning, when player numbers are at their lowest too).
Making everyone else look sober.