If you want to be able to see the New Zealand public holiday dates, including all the regional anniversaries, alongside your electronic calendar, you can access them in iCalendar format (external link) .
iCalendar format is a standard for calendar data exchange. It enables publishing of calendars or schedules on the web, which can then be viewed by a compatible calendar program. Common calendaring programs include Mozilla Sunbird and Lightning (open source), Microsoft Outlook, Apple iCal and Google Calendar.
Modern calendar programs will periodically download the iCalendar data anew, to receive new and updated events. iCalendar functions as a data feed, conceptually similar to when you 'subscribe' to an RSS feed. This is in contrast to the older concept of 'importing' a calendar which is a one-time process to load a snapshot of a calendar as it exists at a point in time. Some older calendar programs (including Outlook 2003) allow you to import iCalendar data, but will not 'subscribe'.
By subscribing to iCalendar feeds you can view the up-to-date status of multiple calendars which may be overlaid against your own personal calendar.
1. RFC 5545 (external link) , sometimes referred to as 'iCal'