Auckland is the only city in New Zealand that has direct, non-stop flights from North America. From there you will find several connections a day to the two other major airports, Wellington and Christchurch. The flying time from Los Angeles to Auckland is approximately 12 hours 45 minutes.
The low season for fares is currently April 17 to August 23; shoulder season runs from August 24 to December 8 and through most of March and April; high season is December 9 to March 5