In the town scene, a Chrysler PT Cruiser is clearly visible. This vehicle was manufactured from 2001.
When David Gray is crossing the street to go to the bank, there is a sign on a shop in the background for the TAB, but it is clearly the new logo, not the one which was used back in 1990 when this film is meant to take place.
As David Gray is seen walking through the main city centre, vehicles passing and parked on the side of the road are shown to have their rectangle shaped registration labels on the bottom left of the inside of the windscreen. This system was not implemented by Land Transport New Zealand until 1996. Before this, registration stickers were small and placed on the outside of the top middle of the windscreen.
The roads at Aramoana and the road to Port Chalmers were all unsealed gravel in 1990. The subsequently sealed roads are visible in the film, like when Bryson is fleeing Gray in the van, and when Guthrie and Anderson arrive in Aramoana.
When Guthrie is on the radio while driving to Aramoana he says David Gray is 37. Gray was 33 at the time.