The Chatham Islands Territory is a group of about ten islands that lies 650 km (500 miles) to the east of the south island of New Zealand. The islands have been part of New Zealand since 1842. 

Like several other provinces, the date of Provincial Anniversary Day marks the arrival of the first European ships to the region.  

On 29 November 1791, captain William R. Broughton from the HMS Chatham of the Vancouver Expedition landed on the islands, claiming them for Great Britain. Captain Broughton named the islands after his ship. 

On arrival, the British found the islands inhabited by the Moriori, a Polynesian tribe that had settled on the islands in the sixteenth century. 

Even though the anniversary of the arrival of the British was on 29 November, the Anniversary is observed on the Monday nearest 30 November. 

The Holidays Act 1981 specifies each locality observing a Provincial Anniversary Day to celebrate the founding days or landing days of the first colonists of the various colonial provinces. 

However the exact dates are not legislated for. The actual observance days can vary even within each province and is due to local custom, convenience or the proximity of seasonal events or other holidays. This may differ from the official observance day, and may be several weeks from the official day.