Starting in 2035, no extra seconds will be added to synchronize clocks with astronomical time
At the General Conference on Weights and Measures, it was decided, from at least 2035, to discontinue the periodic synchronization of atomic clocks of world reference with the astronomical time of the Earth.
This is due to the inhomogeneity of the Earth's rotation, astronomical clocks are slightly behind the reference ones, and to synchronize exact time, starting in 1972, atomic clocks were suspended by a second every few years, as soon as the difference between the reference and astronomical clock time reached 0,9 seconds (the last correction of this type was 8 years ago).
Now, starting in 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 movement of the Earth's rotation gradually slows down due to the influence of the Moon's gravity, and the intervals between synchronizations decrease with time, for example, if the dynamics were maintained after 2000 years, one would have to wait for a new second to be added each month.
Deviations in the Earth's rotation parameters are random in nature and its change, observed in recent years, can lead to the need not to add, but to subtract an extra second.
As an alternative to second-by-second synchronization, the possibility of synchronization with accumulation of changes is contemplated by 1 minute or 1 hour, which will require time correction every several centuries. The final decision on the additional synchronization method is expected to be made before 2026.
The decision to suspend timing per second was due to numerous glitches in software systems related to the fact that during synchronization 61 seconds appeared in one of the minutes. In 2012, such synchronization caused massive failures in server systems that were configured to synchronize the exact time using the NTP protocol.
Due to an unwillingness to handle the appearance of an extra second, some systems got stuck in a loop and started consuming unnecessary CPU resources. In the next synchronization, which happened in 2015, it seemed that the past sad experience was taken into account, but in the linux kernel, during preliminary tests, a bug was found (fixed before sync), which caused some timers to run one second ahead of schedule.
Although in the long term the Earth's rotation is slowing as a result of the Moon's pull, an acceleration since 2020 has also made the problem more pressing because, for the first time, a leap second may need to be removed, instead of added. UTC it's only had to slow down for a second to wait for Earth, not skip to catch up. "It's described as a Y2K problem, because it's something we've never had to deal with," says Donley, referencing computer bugs that were expected to occur in the early 2000s.
Given that 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 emergency (in the time since the last synchronization, they manage to forget about the problem and implement code that does not take into account the characteristic in question).
Problems also arise in financial and industrial systems, that require accurate time tracking of work processes. It is noteworthy that errors associated with an extra second appear not only at the time of synchronization, but also at other times, for example, a bug in the code to correct the appearance of an extra second in GPSD caused a time shift of 1024 weeks in October 2021. It's hard to imagine what anomalies not to add to, but subtracting a second can lead.
Interestingly, synchronization termination has a drawback, which can affect the operation of systems designed for the same UTC and UT1 times. Problems can arise in astronomical (for example, when adjusting telescopes) and satellite systems.
Source: https://www.nature.com/