Timekeepers are adding an extra second Saturday at midnight - a leap second - so you might want to count down from 11 on New Year's Eve to be precise.
The scientists who keep track of international time say it's necessary to add the second to keep the world's atomic clocks in sync with the Earth's own rotation, which fluctuates unpredictably and is less stable than our technology.
There have been 26 leap seconds added to the clock since 1972.