At the General Conference on Weights and Measures, it was decided, starting at least from 2035, to suspend the periodic synchronization of the world's reference atomic clocks with the Earth's astronomical time. Due to the inhomogeneity of the Earth's rotation, astronomical clocks are slightly behind the reference ones, and in order to synchronize the exact time, starting from 1972, atomic clocks were suspended for one second every few years, as soon as the difference between the reference and astronomical time reached 0.9 seconds (the last such correction was 8 years back). From 2035 synchronization will cease and the difference between Coordinated Universal Time (UTC) and astronomical time (UT1, mean solar time) will accumulate.
The issue of stopping the addition of an extra second has been discussed at the International Bureau of Weights and Measures since 2005, but the decision has been constantly postponed. In the long term, the rotation of the Earth's motion gradually slows down due to the influence of the Moon's gravity and the intervals between synchronization are reduced over time, for example, if the dynamics were maintained after 2000 years, a new second would have to be added every month. At the same time, the deviations of the parameters of the Earth's rotation are random in nature, and the dynamics have changed over the past few years and the question arose of the need not to add, but to subtract an extra second.
As an alternative to second-by-second synchronization, the possibility of synchronization is considered with the accumulation of changes for 1 minute or 1 hour, which will require time correction every several centuries. The final decision on the method of further synchronization is planned to be made before 2026.
The decision to suspend per-second synchronization was due to numerous failures in software systems related to the fact that during synchronization, 61 seconds appeared in one of the minutes. In 2012, such synchronization led to massive failures in server systems that were configured to synchronize the exact time using the NTP protocol. Due to the unwillingness to handle the appearance of an extra second, some systems got stuck in a loop and began to consume unnecessary CPU resources. The next synchronization, which took place in 2015, seemed to take into account the sad past experience, but in the Linux kernel, during the preliminary tests, a bug was found (fixed before synchronization), which led to the operation of some timers a second ahead of schedule.
Since most public NTP servers continue to give an extra second as is, without blurring it into a series of intervals, each synchronization of the reference clock is perceived as an unpredictable rush that can lead to unpredictable problems (in the time since the last synchronization, they manage to forget about the problem and inject the code , which does not take into account the feature under consideration). Problems also arise in financial and industrial systems, which require accurate time tracking of work processes. It is noteworthy that errors associated with an extra second pop up not only during synchronization, but also at other times, for example, an error in the code for correcting the appearance of an extra second in GPSD led to a time shift of 2021 weeks in October 1024. It is difficult to imagine what anomalies not adding, but subtracting a second can lead to.
Interestingly, the cessation of synchronization has a downside, which can affect the operation of systems designed for the same UTC and UT1 hours. Problems can arise in astronomical (for example, when adjusting telescopes) and satellite systems. For example, representatives of Russia voted against the suspension of synchronization in 2035, who proposed to move the suspension to 2040, since the change requires a significant reworking of the infrastructure of the GLONASS satellite navigation system. The GLONASS system was originally designed to include leap seconds, while GPS, BeiDou and Galileo simply ignore them.
Source: opennet.ru