Scientists and government officials meeting at a conference in France on Friday voted to eliminate leap seconds by 2035, the organization responsible for global timekeeping said.
Similar to leap years, leap seconds have been regularly added to clocks over the past half-century to compensate for the difference between exact atomic time and the Earth’s slower rotation.
While leap seconds pass unnoticed by most people, they can cause problems for a range of systems that require precise, uninterrupted flow of time, such as satellite navigation, software, telecommunications, commerce, and even space travel.
It’s been a headache for the International Bureau of Weights and Measures (BIPM), which is responsible for Coordinated Universal Time (UTC) – the internationally agreed standard by which the world sets its clocks.
A resolution to stop adding leap seconds by 2035 was passed by BIPM members and others at the 27th General Conference on Weights and Measures, held roughly every four years at the Palace of Versailles, west of Paris.
The head of the BIPM’s time department, Patrizia Tavella, said the “historic decision” would “enable a continuous flow of seconds without the discontinuities currently caused by irregular leap seconds”.
“The change will take effect by or before 2035,” she told AFP via email.
“The connection between UTC and the Earth’s rotation is not lost, UTC remains Earth-related,” she said, adding that for the public “nothing will change.”
– A leap minute? –
Seconds have long been measured by astronomers analyzing the Earth’s rotation, but the advent of atomic clocks – which use the frequency of atoms as a tick-tock mechanism – ushered in a much more precise era of timekeeping.
The problem is that the Earth’s slightly slower rotation means the two times are not in sync.
To fill the gap, leap seconds were introduced in 1972, and since then 27 have been added at irregular intervals – the last in 2016.
After the suggestion, leap seconds are added as usual for now.
From about 2035, the difference between atomic and astronomical time is allowed to grow to more than a second, Judah Levine, a physicist at the US National Institute of Standards and Technology, told AFP.
“The greater value has yet to be determined,” said Levine, who helped draft the resolution alongside Tavella for years.
Negotiations are ongoing to come up with a proposal by 2035 to determine that value and how it will be managed, the resolution said.
The breakdown of countries that voted in favor of the resolution was not yet known, but the United States and France were among the trailblazers for the change.
Levine said it’s important to protect UTC time because it’s driven by “a global community effort” in the BIPM, which has 59 member states and consults with other nations.
GPS time, a potential UTC rival controlled by atomic clocks, is operated by the US military “without global oversight,” Levine said.
A possible solution to the problem could be to increase the discrepancy between the Earth’s rotation and atomic time to one minute.
It’s difficult to say exactly how often that might be necessary, but Levine estimated somewhere between 50 and 100 years.
Then, instead of adding a leap minute to clocks, Levine proposed a “kind of smear” where the last minute of the day lasts two minutes.
“The advance of a clock slows but never stops,” he said.
