It means that from 2035, or possibly earlier, astronomical time (known as UT1) will be allowed to diverge by more than one second from coordinated universal time (UTC), which is based on the steady tick of atomic clocks.Extreme numbers get new namesStopping the adjustments is “a leap forward” for researchers who work on time and frequency, says Georgette Macdonald, director general of the Metrology Research Centre in Halifax, Canada.Astronomers who rely on UT1 to align their telescopes will also need to adjust, says Elizabeth Donley, who leads the Time and Frequency division at the National Institute of Standards and Technology, in Boulder, Colorado.The body effectively ceded decision making about the leap second to the CGPM in 2015, and Arias says its working group agreed with the CGPM’s proposal.“This is the thing that makes us a little bit nervous.”Subtle differenceAlthough human timepieces have been calibrated with Earth’s rotation for millennia, most people will feel little effect from the loss of the leap second."