Two prominent Maori academics have suggested we're using the wrong month - and the wrong calendar - to celebrate the traditional start of the Maori new year.
Each year, the appearance of the star cluster Te Iwa o Matariki in the morning skies comes with the dawning of the Maori new year, and coincides with celebrations and festivals around the country.
Since the tradition was revived at the start of the millennium, Matariki has been marked in June, around the time the cluster begins to rise.
But this year, acclaimed Waikato University astronomer Dr Rangi Matamua and Paraone Gloyne, a Maori language expert at Te Wananga o Aotearoa, argue festivities would be more appropriately held around July 17.
Matamua said a misconception about Matariki had been partly created by using the 365-day Gregorian calendar and not the 354-day year lunar calendar that Polynesians long relied upon.
This led to an 11-day shortfall between the calendars and meant the Gregorian calendar could not accurately determine when Matariki would rise according to Maori tradition.
"We've kind of smashed it into the solar calendar and they are two incompatible systems - but we haven't revived the system of time we use to observe Matariki," said Matamua, who recently published the book Matariki: The Star of the Year.
"There are good nights and bad nights in the lunar calendar, and the research I have worked on shows the most productive nights of the lunar phase are the Tangaroa nights, or the last quarter."
This year, the beginning of the Tangaroa phase - or the three or four days leading to the new moon - begins on July 17.
"So it's a triangulation of getting the right month with the right lunar phase - and then you go out and celebrate," Matamua said.
"I think we do the celebrations really well, but I'd love for us to return to the Matariki system of time, to make sure that our celebrations coincide with the correct date."
Gloyne said some had suggested the timing of Matariki this year was in early to mid June - yet this was when the phase of the moon was "whiro".
"Whiro is not when Maori would traditionally observe Matariki - Whiro is associated with negative energy, bad stuff, and destruction, why would you want to celebrate Matariki during Whiro?"
Gloyne said ancient cultures relied upon the lunar calendar to determine when their festivals and other significant events would be held - and Maori dependence on it was no different.
"The Muslim faith hold Ramadan based on the lunar calendar as do the Chinese with their new year celebrations.
"We've nurtured a culture of the blind following the blind in relation to the rising of Matariki."
Charles Royal, director of the Matariki Rising Festival, said celebrations throughout the country had now taken place during June for many years, and it would "take a little while" to alter the timing.
"Nonetheless, it is important to continue to increase the cultural and thematic integrity of this distinctively Aotearoa-New Zealand celebration and Dr Matamua's work is a great help in this regard."
However, respected Auckland astronomer Dr Grant Christie said not all Maori traditionally used the same system to start the new year: some used full moon phases, while others didn't use Matariki, but the star Puanga, or Rigel.
"You can argue if you want to that July is okay to have Matariki, but in terms of government policy, for the whole country they've got to come up with a compromise - different Maori groups may or may not agree with that but that's not an astronomical question.
"So, essentially, you could have the whole conversation without reference to the Gregorian calendar ... but the issue comes down to different tribes as to whether they use the full moon or the new moon to restart."