A "leap second" will be added to 2016 to compensate for a slowdown in the Earth's rotation.
Time will gain a second before midnight on December 31, 2016. Photo: 123RF
The extra second will occur as clocks strike midnight UTC time, delaying 2017 momentarily.
For New Zealand, that will be just before 1pm on New Year's Day. RNZ listeners may notice an extra pip at the top of the hour before the news.
This will be the 27th time a leap second has been required - the last one was in June 2015.
The change was needed because standard time lagged behind that recorded by super-accurate atomic clocks.
Britain's National Physical Laboratory uses an atomic clock to provide a stable and continuous timescale.
Senior research scientist Peter Whibberley said leap seconds were needed to prevent civil time drifting away from Earth time.
Callaghan Innovation in Lower Hutt is home to the country's three atomoic clocks, which are responsible for keeping New Zealand's time.
Measurement scientist Adam Dunford said the clocks were unassuming boxes - about the size of a desk top computer - but they kept time to about 9 billion ticks a second.