Ruhanui: The 13th Month
Every 3 years, the month of Ruhanui is added to our maramataka.
What is Ruhanui?
Ruhanui is an ‘extra’ lunar month added to our maramataka after Te Tahi o Pipiri every third year. But why do we need it?
The lunar year lasts 354 days, which is 11 days shorter than the solar year (365.25 days). To make sure the lunar and solar calendars stay aligned, every third year we add a 33-day month called Ruhanui.
This concept is called intercalation. In timekeeping, intercalation means adding an extra day or month to align with the solar calendar. We use the same concept in our Gregorian calendar with a leap day added in February every 4 years.
Without intercalation, our timekeeping systems would slowly get out of sync with our environment.
Ruhanui is used in our maramataka to realign systems of timekeeping, but some iwi do this in different ways and at different times. We encourage you to learn the system that your hapū or iwi uses for their maramataka.
How does Ruhanui relate to Matariki?
In our maramataka, Matariki is the main tohu (sign) of the new year. When we can see Matariki rise early in the morning in the Tangaroa lunar phase during the month of Pipiri, then we know that a new year has begun.
In the following year, Matariki will sit lower in the sky during the Tangaroa phase of Pipiri due to the 11-day difference between the lunar and solar calendars. The year after that, it will sit even lower in the sky.
Matariki is not a super-bright star cluster. If it doesn’t maintain a certain distance from the horizon relative to the sun, it will get washed out by the sun’s light and we won’t be able to see it with the naked eye. Our tūpuna knew when they couldn’t see Matariki rise during the Tangaroa phase of Pipiri that it was time to insert the extra lunar month: Ruhanui.
The addition of the ‘extra’ month allows for our timekeeping system to realign the lunar and solar calendars. By the time the Tangaroa phase of Ruhanui arrives, the movement of the solar system positions the Matariki star cluster and the sun such that we can observe Matariki with the naked eye again.
That’s why we celebrate Matariki when it rises during the Tangaroa lunar phase of Ruhanui, instead of Pipiri, every third year in our maramataka. It realigns the lunar and solar calendars for the next 3-year cycle, which we call Te Tau Toru Nui o Matariki.
Source: Living by the Stars with Professor Rangi Matamua, “When to celebrate Matariki”