In 2022 Aotearoa New Zealand made Matariki a public holiday, the first anywhere in the country tied to an indigenous observance, and the way the date is set is the interesting part. It is not fixed to a day of the month and it is not the nearest convenient Monday to something. An advisory group of Maori astronomers and knowledge holders determines it from the Maori lunar calendar against the rising of the cluster, and the dates have been published years ahead on that basis.
That is a state adopting another calendrical system rather than translating one into its own. The holiday moves through late June and July, and the reason it moves is astronomical and cultural rather than administrative.
Not everyone reckons from Matariki. Some iwi, particularly in the far north and on parts of the east coast, mark the new year from Puanga, the star Rigel, either because Matariki is difficult to see from their horizon or because that is simply their tradition. The holiday legislation and the public material acknowledge this rather than flattening it, which is a small thing that matters.
The revival has also driven a considerable amount of documentation. Maori astronomical knowledge that existed in a few hands twenty-five years ago is now taught in schools, and that is a direct consequence of the holiday.