Ardern says it's a public holiday that's time has come.
"It's unique to New Zealand, it's representative of the Māori new year, and of course over recent years there have been greater and greater calls for us to embed that in our calendar."
She says starting it in 2022 balances the cost to businesses, and the boost it may give the tourism sector.
Ardern acknowledges there have also been calls to make Parihaka - November 5 - a commemorative holiday.
She says teaching New Zealand history in schools has been a way to respond to those calls.
"For Parihaka, we've made investment through the Provincial Growth Fund to make sure we are regionally showcasing and acknowledging the history of that part of the region and also its role within New Zealand history."
She says in each area, Labour has been working to lift the profile of "those different parts of our history and our culture, and hopefully getting the balance right between all of them".
"Matariki is something that does bring together different regions, different areas across the country.
Prime Minister Jacinda Ardern. Photo / Andrew Warner
"It is a chance for us, in the middle of winter, to have a moment of celebration."
She says Matariki has the power to bring the country together and acknowledge "who we are".
"When you think of our public holiday landscape at the moment, there's not many, if any, that really do that other than the acknowledgement of Waitangi Day."
We pivot to child poverty - a topic Ardern has said before is one of her biggest issues - and an issue in Rotorua.
She lists what was achieved in the first 100 days of Government - "that families package which introduced a new universal payment for children in the first year of their life… we also extended paid parental leave... we increased paid parental leave as a payment… we also increased the family tax credit, we have indexed benefits to wages, we have increased general benefit rates by $25 a week and we introduced the winter energy payment".
"Taken as a whole, those are the most significant reforms for those on low and middle incomes that New Zealand has had for decades and it will, and is making a dent in child poverty.
"We've made a good start, we need to do more though."
There was the lunches in schools programme too, which had been extended, she says.
Last week, New Zealand ranked near the bottom of a Unicef league table ranking OECD countries on child wellbeing.
Yesterday Children's Commissioner Judge Andrew Becroft told me the Government had put "more in place than has ever been done for 30 years" to rectify issues of child poverty related to the 1991 "Mother of All Budgets" cut to benefits.
However, he said there was still a call for an increase to benefits in the realm of, broadly speaking, $75-$100 a week, echoing a recommendation by the Welfare Expert Advisory Group.
