Well daylight saving in NZ is now well entrenched-but goes back a long time-longer than most would think. 1868 NZ standard time was set at 11h30m ahead of GMT. In 1927 daylight saving was first observed in NZ-but varying dates and degrees over subsequent years. Ignoring temporary emergency regulation during the war years, in 1946 NZ summer time of +12hrs GMT was adopted as NZ standard time-thus incorporating 30 minutes of daylight saving permanently-and daylight saving summer time reintroduced in 1975. So as I type this the time is 1-1/2 hours ahead of what it would have been on this date in 1867!
In any case the International dateline is partially to blame....and it's anything but straight! See:
https://en.wikipedia.org/wiki/International_Date_Line