I don’t see seats sales everyday from Air New Zealand (this is still probably a good time to visit not as good as January though!)

ANZNew-Year-Sale-2015

This special applies to all cabins, including Economy, Premium Economy and Business Premier.

New Year’s Sale
Promo CodePromotionValid for Travel
NY300CSave $300* to the South Pacific (New Zealand, Cook Islands and Australia)12 January – 30 September, 2015
Sample Fares
Origin – DestinationValid for TravelSale Price
Vancouver – Auckland13 May – 3 June & 24 July – 21 Sep, 2015$1,148
Vancouver – Sydney01 May – 21 Jun, 01 Aug – 17 Sep, 2015$1,149
Vancouver – Rarotonga26 Apr – 5 Jul, 2015$874 

Here is the link to the promo page.

This deal ends January 7, 2015.

Use the promo code NY300C for a $300 discount off adult base fares booked in Economy, Premium Economy, and Business Premier class between Canada and Australia, New Zealand, and Cook Islands. Offer only applies to return bookings purchased from airnewzealand.ca. Offer is valid for sale between 01 Jan, 2015 and 07 Jan, 2015 for travel between 12 Jan, 2015  and 30 Sep, 2015. Only one promo code per purchase is permitted.