The world’s official timekeepers have added a “leap second” to the last day of the year on Wednesday, to help match clocks to the Earth’s slowing spin on its axis, which takes place at ever-changing rates affected by tides and other factors.
The U.S. Naval Observatory, keeper of the Pentagon’s master clock, said it would add the extra second on Wednesday in coordination with the world’s atomic clocks at 23 hours, 59 minutes and 59 seconds Coordinated Universal Time, or UTC.
UTC is the time scale kept by highly precise atomic clocks around the world, accurate to about a billionth of a second per day, the Naval Observatory says. For those with a need for precision timing, it has replaced Greenwich Mean Time, or GMT.
