The time has come – or will come, in 2035 – to drop the leap second.
So the member countries of the International Convention on Science and Measurement Standards voted on Friday at a meeting in Versailles, France. The near-unanimous vote on what was known as Resolution D was met with relief and jubilation by the world’s metrologists, some of whom have been pushing for a solution to the leap second problem for decades.
“Incredible,” Patrizia Tavella, director of the time division of the International Bureau of Weights and Measures, known as BIPM from its French name and based outside Paris, wrote in a WhatsApp message shortly after the vote. “More than 20 years of consultation and now a nice agreement.” She added that she was “moved to tears”.
The United States was a staunch supporter of the resolution. “It feels like a historic day,” said Elizabeth Donley, chief of the time and frequency division at the National Institute of Standards and Technology, or NIST, in Boulder, Colo. “And I wish I was there. There’s probably a lot of celebrating in style.”
The leap second has caused problems since its inception 50 years ago. It was devised as a way to match the International Atomic Time Scale, in use since 1967 and derived from the vibration of cesium atoms, to the slightly slower time the Earth maintains as it rotates. In fact, when atomic time is one second ahead, it stops one second to allow Earth to catch up. When the fudge was unveiled in 1972, ten leap seconds were added to the atomic time scale. Twenty-seven more have been added since then.
Those extra seconds were hard to fit in in 1972; today the technical issues are gnarly. First, it’s hard to predict exactly when the next leap second will be needed, so computer networks can’t prepare for orderly, regular insertions. Different networks have developed their own, uncoordinated methods for building in the extra second.
In addition, modern global computing systems have become more closely intertwined and dependent on hyper-precise timing, sometimes down to the billionth of a second. Adding the extra second increases the risk that those systems responsible for telecommunications networks, power transmission, financial transactions and other vital businesses will crash or fail to sync.
As a result, unofficial time systems have slowly begun to supplant the world’s official international time, Coordinated Universal Time, or UTC. interrupted episodically.
“The main problem is preserving the concept that time is an international quantity,” said Judah Levine, a physicist at NIST. He called the Versailles decision “an incredible step forward.”
Russia voted against the resolution; Belarus abstained from voting. Russia has long tried to delay giving up the leap second because its GLONASS global navigation satellite system includes the extra seconds, unlike other systems such as GPS, which is operated by the United States. With Russia’s concerns in mind, the leap second will not be dropped until 2035, although it could happen sooner.
Resolution D calls for UTC to go unbroken through leap seconds from 2035 to at least 2135 and for metrologists to eventually figure out how to reconcile the atomic and astronomical time scales with fewer headaches. The international time standard would be separated from time for generations to come, as told by heaven.
But bringing those two time scales back together was imperative, said Rev. Pavel Gabor, an astrophysicist and the vice director of the Vatican Observatory Research Group in Tucson, Ariz. He said atomic timekeeping was just one example of how the world became unintelligible to the average person, and that scientists had a responsibility to help people take control of their lives.
“I think sensitivity to this distrust of elites, distrust of experts, distrust of science and institutions, is something that is a very real problem in today’s world,” he said. “And let’s not contribute to it.”
There are still steps towards abolishing the leap second. While BIPM is responsible for universal time, the International Telecommunication Union, or ITU, is responsible for transmitting it. The ITU’s World Radiocommunication Conference in Dubai, United Arab Emirates, will also vote on the issue next year. Felicitas Arias, the former director of BIPM’s time division and now a visiting astronomer at the Paris Observatory, said negotiations between the two organizations convinced her that the ITU will support the Versailles vote.
“Now we’re really seeing the moment getting closer to having continuous time,” she said, applauding Friday’s vote. “And this is something we’ve been dreaming about for a long time.”
