It’s a good idea to keep your system software up to date. Even so, sometimes Apple lets us down, as they did with the change to daylight savings in New Zealand this year. (Daylight Savings early in 2007)
Finally we have word that they’ve fixed the problem: Mac OS X: Adjusting Date & Time for New Zealand’s late 2007 Daylight Saving Time changes:
In the second half of 2007, New Zealand began observing 27 weeks of Daylight Saving Time each summer. These new Daylight Saving Time rules are included in Mac OS X 10.4.11 and Mac OS X 10.5 Leopard.