Matariki is the Pleiades in Maori reckoning, and the year begins when the cluster is first seen rising in the east just before sunrise, in the depth of winter. The event is not a date on a calendar that happens to fall in June. It is an observation, and it is made by people who go out in the dark and look.
What is done with it has three parts, and they are usually given in that order. The dead of the past year are remembered and released, their names called to the stars. The present is marked with food, since the harvest is in and the storehouses are full. And the year ahead is set: what will be planted, what is intended, what is hoped for.
The individual stars were read as well as the cluster. Different accounts assign them to fresh water, salt water, the forest, the cultivated crops, the winds and the dead, and their relative clarity on the morning of the rising was taken as an indication of how each domain would fare in the season coming.
Observance was heavily suppressed and had almost stopped by the mid twentieth century, surviving in a few places and in the memory of a few people. Its revival from the 1990s onward was deliberate, led by Maori scholars and communities, and it moved quickly.