Not just a moment: the abolition of leap seconds will complicate the launch of air taxis and unmanned vehicles

As early as 2027, the approach to calculating world time may change. Scientists have decided to abandon the usual leap seconds, which have been added to world time for decades to compensate for the uneven rotation of the Earth. The reason is not only the malfunction of servers, digital platforms and exchanges, but also the unexpected acceleration of the planet's rotation. In the future, this may require not adding, but subtracting a whole second. Now, instead of frequent corrections, humanity is ready to accumulate the discrepancy for centuries — until it reaches an hour. Russian experts note that for most people these changes will remain unnoticeable. However, with the development of air taxis and self-driving cars, the accuracy of time synchronization will become even more important: even split-second errors can lead to accidents. Therefore, after changing the order of time calculation, it will be necessary to adapt the software of the corresponding systems.

Canceling leap seconds

On October 15, the participants of the 28th General Conference of Weights and Measures (CGPM) in Versailles decided to switch from periodic corrections to longer time correction intervals.

Now, to compensate for the discrepancy between the readings of ultra-precise atomic clocks and the actual speed of the Earth's rotation, an additional second is added to Coordinated Universal Time (UTC) approximately once every two years. However, such adjustments can cause disruptions to transport schedules, navigation systems, servers, and exchanges. Therefore, the scientists decided that now corrections will be made only after the discrepancy reaches an hour. It is estimated that this may happen no earlier than in a thousand years.

— The leap second was introduced by the Paris Observatory in 1972. Over these 50—plus years, only 27 leap seconds have been added - about one every two years. But even it creates serious disruptions in the operation of digital platforms and servers," Professor, current president of the French Academy of Sciences, Chairman of the General Conference of Weights and Measures Francoise Combe told Izvestia.

The problem of time adjustment has become more acute against the background of the discovery of changes in the speed of rotation of the Earth. Scientists have found that the planet is not only slowing down, which requires the addition of leap seconds, but also periodically accelerates.

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— Therefore, it may be necessary to introduce a negative leap second — that is, to subtract one second. And this would create real chaos, since the software is not prepared for such a scenario. Since 1972, only positive leap seconds have been introduced, meaning seconds have been added rather than subtracted. A negative leap second would be a real nightmare for specialists," said Francoise Combet.

To avoid such a scenario, CGPM decided to switch to the new system as early as May 2027, the head of the organization noted.

However, this decision has its opponents. Leap seconds have been around for decades and have become part of many technological systems, from atomic clocks and satellite navigation to banking infrastructure.

— It is unclear why to fix something that is not broken. For example, space systems and satellite technologies, including the Russian GLONASS system, have been successfully operating with leap seconds for many years. But if a negative leap second needs to be introduced, some developers will have to rethink the architecture of their systems, take extra care, and possibly redesign them. A similar situation has already arisen in the run—up to 2000, when it was feared that computers would fail," says Marek Siebart, professor of space geodesy at University College London.

Now, companies responsible for television broadcasting, radio stations, and computer networks will have to check whether abandoning leap seconds will cause their systems to malfunction. At the same time, the arguments against changing the current order largely come from large corporations, Marek Siebart warned.

Consequences of the scientists' decision

With the development of high-precision instruments for measuring time, it became obvious that the rotation of the Earth and other celestial bodies, which was used in calculations, occurs unevenly. To account for these fluctuations and synchronize coordinated universal time with astronomical time, a leap second was introduced, astrophysicist and science popularizer Vladimir Afanasyev explained to Izvestia.

— Accurate timing is necessary, for example, to monitor the safety of large engineering structures such as dams, bridges and skyscrapers. It is important to ensure strict time binding of data coming from sensors distributed throughout the structure. Such synchronization is also needed in industrial Internet of Things systems that combine multiple devices. In high—frequency trading, accounting for microsecond intervals helps prevent market manipulation," the scientist said.

Now these processes are practically invisible to the population. However, with the proliferation of air taxis and self-driving cars, accurate time synchronization will become even more important: even split-second errors can lead to accidents, he noted. After canceling the leap second, the software will need to be adjusted to account for the discrepancy between astronomical and world time. In his opinion, it is better not to accumulate errors, because sooner or later they will still have to be taken into account.

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— When 23:59:59 is followed by 23:59:60 and only then by 00:00:00, this creates an unusual situation for computer systems. Over the decades, developers have become accustomed to this practice in many ways, and most mission-critical systems have already been debugged. However, in the coming years, there is a significant possibility that a second will have to be subtracted rather than added. Such a case would be unprecedented, and it is not known in advance how critical systems will react to it," commented Dmitry Tregubov, Senior researcher at the Laboratory Optics of Complex Quantum Systems at the Lebedev Physical Institute of the Russian Academy of Sciences.

According to the expert, this is another argument in favor of abandoning leap seconds. Such a decision, for example, will complicate the work of scientists engaged in astronomical observations: they will have to take into account the gradually growing discrepancy between astronomical and world time and calibrate the equipment accordingly. But the work of exchanges and digital services will become more stable. If earlier people hardly noticed the addition of a leap second, then the "leap hour", which may need to be introduced in a few centuries or later, will become a landmark event.

— Adding a leap second will not affect the operation of satellite navigation equipment and the ERA-GLONASS state information system. For modern digital systems and global positioning equipment, synchronization is carried out not only by satellite signals, but also using ground—based special equipment, reference time sources and secure data transmission channels," said Mikhail Korablev, General Designer of GLONASS.

According to him, failures related to the addition of leap seconds did occur in the early 2000s, when many digital platforms and servers were not ready to correctly process such corrections. However, modern time accounting and synchronization systems, as well as infrastructure management, take this feature into account at the architecture and software levels.