leap second
noun
: an intercalary second added to Coordinated Universal Time to compensate for the slowing of the earth's rotation and keep Coordinated Universal Time in synchrony with solar time
Example Sentences
Recent Examples on the Web If those measurements get too out of sync, the International Earth Rotation and Reference Systems Service, an organization that maintains global time, may fix the discrepancy by adding a leap second. 
CBS News, 13 Aug. 2022 This January, the International Earth Rotation and Reference Systems Service ruled out the possibility of introducing a leap second at the end of June. Christine Mui, Fortune, 4 Aug. 2022 Because Earth is now rotating faster, a leap second would need to be taken away to catch our timekeeping up with Earth's increasing rotational speed, McCarthy said. Megan Marples, CNN, 8 Aug. 2022 Leap seconds have been added in the past – the first leap second was added was in 1972, and they're typically added in June or December. Sarah Raza, USA TODAY, 5 Aug. 2022 With the reversal of that trend in the past years, the last time a positive leap second was added was on the last day of 2016. Christine Mui, Fortune, 4 Aug. 2022 As opposed to leap years, which have an extra day added, a negative leap second would mean clocks skip one second. Caitlin O'kane, CBS News, 3 Aug. 2022 Leap seconds have been added in the past; first leap second was added was in 1972, and they're typically added in June or December. Sarah Raza, Detroit Free Press, 3 Aug. 2022 The first leap second was added back in 1972, with 26 more being added throughout the last several decades. Joshua Hawkins, BGR, 2 Aug. 2022 See More
CBS News, 13 Aug. 2022 This January, the International Earth Rotation and Reference Systems Service ruled out the possibility of introducing a leap second at the end of June. Christine Mui, Fortune, 4 Aug. 2022 Because Earth is now rotating faster, a leap second would need to be taken away to catch our timekeeping up with Earth's increasing rotational speed, McCarthy said. Megan Marples, CNN, 8 Aug. 2022 Leap seconds have been added in the past – the first leap second was added was in 1972, and they're typically added in June or December. Sarah Raza, USA TODAY, 5 Aug. 2022 With the reversal of that trend in the past years, the last time a positive leap second was added was on the last day of 2016. Christine Mui, Fortune, 4 Aug. 2022 As opposed to leap years, which have an extra day added, a negative leap second would mean clocks skip one second. Caitlin O'kane, CBS News, 3 Aug. 2022 Leap seconds have been added in the past; first leap second was added was in 1972, and they're typically added in June or December. Sarah Raza, Detroit Free Press, 3 Aug. 2022 The first leap second was added back in 1972, with 26 more being added throughout the last several decades. Joshua Hawkins, BGR, 2 Aug. 2022 See More Word History
First Known Use
1971, in the meaning defined above