I’ve been researching how to minimize the effects of jet lag since it’s about a 24 hour flight from NYC. I found one well traveled gentlemen who wrote:
“One trick that works for me is to set my watch to destination time as soon as I board the first plane and I start to think in terms of what time it is "there" as the trip progresses. That way my mind is already acclimated to the local situation when I arrive and it assists in convincing my body into believing the same!!!
I've also found it psychologically less stressful to approach the US East Coast to NZ trip in generic terms, rather than by counting the hours (or calendar days). As in: leave JFK in the afternoon, take off from LAX in the evening, fly overnight, and land in AKL early the next morning. Sounds simple, doesn't it? A lot better than thinking hard about 18+ flying hours, + 2 days!!! Look at it this way - when you come back - it'll hardly take any time!!!”
Other tips that sounded reasonable were:
Gradually adjust your schedule before you leave
Instead of sleeping pills, bring herbal tea bags like Sleepytime
For more on how to best handle a long flight, check this article.