The Sir Peter Blake Torbay Regatta is always on the first full weekend of December.
The 2017 Edition is on the 2nd-3rd December

Torbay hosts New Zealand’s largest annual centreboard regatta – The Sir Peter Blake Torbay Regatta.
This amazing regatta attracts approx 400 sailors and 19 classes every year, it is a fantastic 2 day event that is the highlight of the New Zealand sailing calendar. It has a size and spectacle that is unmatched in the southern hemisphere.

The Sir Peter Blake Regatta has its own event website