EXTRA TIME

Clocks Pause at Midnight for Leap Second

For Earth clocks to catch up to atomic clocks.

Clocks around the world will stop for one whole second at midnight on Tuesday, when the Earth gains one “leap second.” The extra second, a result of the Earth’s orbit gradually slowing down due to moon drag, allows Earth’s clocks to catch up to atomic clocks. The last time a “leap second” was added to the clock in 2012, several Internet companies, including Mozilla, Reddit and LinkedIn, all crashed, along with an airline flight’s check-in system. Markets are also worried, since this is the first time a second has been added during trading hours. A business development manager at the National Physical Laboratory told the Guardian, “If everyone adds the second in the same way at the same time it shouldn’t cause problems. But if some apply it in a different way or at a slightly different time, you start to have discrepancies in the time that people have. That’s when things trip up.”