For further reference I also found a document describing recent changes in visa labels. According to
the document, they previously called it "First entry by:". My guess is that they wanted to resolve the confusion that the entry is permitted also before that day (if my understanding of English is correct, "first entry by" can be also read as "First entry on:"). But now they added another confusion of whether "before" is inclusive the date or not. Again, depending on one's background, "before <the date>" can be read as "before close of business on <the date>", before "before the end of <the date>" or "Before beginning of <the date>" or "not after <the date>" etc. What a mess...
But I also called the visa/immigration service in NZ, they confirmed I should be fine if my plane lands on the same day that visa states as "First entry before".