Upvote:6
It's unlikely there any 'special' flights.
If you're trying to book these on a web site, what you're hitting is just basic data validation in the form itself. The web app checks that 'return date' is equal or later then 'departure date' and doesn't take into account the very small number of flights or travelers that would fly AKL-HNL-AKL in the same day.
If you call the airline directly, they can book this no problem.