Here's a breakdown:
* Pre-European arrival: Māori arrived in New Zealand from Polynesia around 1280 AD, bringing their language with them.
* European arrival: When Europeans arrived in the 17th century, Māori was a well-established and complex language, with distinct dialects and a rich oral tradition.
* Formal recognition: While Māori has always been a living language, it was officially recognized as an official language of New Zealand alongside English in 1987.
Therefore, it's inaccurate to say Māori "became" a language at a specific point in time. It has been a vibrant and integral part of New Zealand's cultural heritage for centuries.