Global timekeepers vote to eliminate leap second by 2035

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 the 59 member states of the BIPM and other parties at the 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, told AFP that the “historic decision” would “allow for a continuous flow of seconds without the discontinuities currently caused by irregular leap seconds.”

“The change will take effect by 2035,” she said via email.

She said Russia voted against the resolution “not on principle” but because Moscow wanted to push back the effective date to 2040.

Other countries have asked for a faster timeframe like 2025 or 2030, so 2035 is the “best compromise,” she said.

The United States and France were among the countries that blazed the trail for change.

Tavella emphasized that “the connection between UTC and the Earth’s rotation is not lost”.

For the public, “nothing will change,” she added.

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 their tick-tock mechanism – ushered in a much more precise era of timekeeping.

But 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.

But by 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 worked alongside Tavella for years in drafting the resolution.

Negotiations are ongoing to come up with a proposal by 2035 to determine that value and how it will be managed, the resolution said.

Levine said it’s important to protect UTC time because it’s driven by “a global community effort” at BIPM.

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 hard to say how long that might last, 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.

© 2022 AFP

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