Seems we’ll all be getting a slightly longer than usual holiday this year:
Officials announce a leap second will be added at the end of December.
The International Earth Rotation and Reference Systems Service in Paris keeps track of time by measuring the Earth’s rotation, which varies, and by an atomic clock, which is unwavering. When a difference in the two clocks shows up, the IERS adds or subtracts a second to the year.
The current standard is a cesium atom, which vibrates 9,192,631,770 times per second. As far as scientists know, this doesn’t change over time and is the same everywhere on Earth and in space.