Happy Waitangi Day to all of you Kiwis out there! For those unfamiliar, it's kind of like New Zealand's version of the Fourth of July — a national day recognizing the creation of the country. A key difference, though, is that the holiday commemorates an 1840 treaty that established British sovereignty over the islands, instead of the United States' holiday centering on the Republic's breaking away from that same monarchy.
The day has not been without its controversy — it does, after all, represent an agreement where the heads of Maori tribes across the islands agreed to be ruled by a crown thousands of miles away. Some see it as a national day of unity, while some activists have called it a fraudulent con job that took away the tribes' rightful territory (the treaty handed over the sole authority to purchase land to the Crown). The disagreement isn't helped by the fact that the Treaty of Waitangi has different text in English from the version written in Maori, and that it's not entirely clear that the chieftains who signed the document fully understood what they were agreeing to, for various reasons. Seems pretty complicated, which is probably why most sources refer to it as a "day of reflection" and not "day of celebration."
You can learn more about Waitangi Day on the official New Zealand History website.