The second-based system is now being removed: A new era in time measurement

A significant change is planned in the timekeeping system that ensures synchronized operation of clocks worldwide. The proposal on the agenda of member countries of the International Bureau of Weights and Measures foresees the termination of the leap second practice that has been used since 1972.

The leap second is used to balance the difference between astronomical time based on Earth's rotation and Coordinated Universal Time (UTC) determined by atomic clocks. However, these irregularly spaced adjustments can cause various problems in digital systems that require precise timing.

Time System Change on the Agenda

The leap second system was developed to maintain harmony between two different timekeeping methods. Because Earth's rotation does not occur at a constant speed, a growing discrepancy can arise between astronomical time and the time shown by atomic clocks.

Since 1972, a total of 27 leap seconds have been added to the global clock system. Although most people do not notice this method in daily life, it is of great importance for computer networks, telecommunications systems, energy infrastructure, and financial transactions.

Earth's Rotation Speed Is Constantly Changing

The Earth does not run like a perfect clock. The planet's rotation speed is affected by various factors such as the Moon's gravity, movements within Earth's interior, and changes in mass distribution on the surface.

The melting of glaciers and the shifting of water masses due to climate change can also affect Earth's rotation. These changes make the calculation of the difference between astronomical time and atomic time more complex.

Although the leap second policy aims to eliminate this difference, the irregular timing of the addition creates a significant technical problem for companies managing digital infrastructure.

Now Leap Seconds Have Caused Disruptions in Technology Systems.

Past leap second additions have caused serious problems in some digital systems. The disruptions in 2012 on social media platforms and flight booking systems brought the technical risks of the practice into focus.

After the final leap second added at the end of 2016, some cloud services also experienced brief outages. Such incidents prompted a reassessment of the practice, especially in systems where timestamps and transactions are executed to second-level precision.

A New Decision Could Be Made in 2027

The 69 member countries of the International Bureau of Weights and Measures, which sets time‑measurement standards, are slated to vote on a proposal concerning the future of the second. If the proposal is accepted, the decision is expected to take effect in May 2027.

In fact, efforts to end the application are not new. The member countries had reached a consensus in 2022 on an approach that envisages the gradual elimination of the second by 2035.

The widespread use of satellite‑based systems such as GPS has also changed the need to rely directly on astronomical time for timekeeping. At the same time, the importance of how the global time standard will be applied and how compatibility between systems will be preserved remains.

The Possibility of Negative Leap Seconds Has Raised Concerns

One of the developments that accelerated the debate was the possibility of negative leap seconds. While Earth's rotation tends to slow down over the long term, short‑term accelerations can still occur.

If this trend continues, it may be necessary to subtract a second from UTC instead of adding one to balance the difference between astronomical time and atomic clocks. This operation, which has not been implemented before, could cause unforeseen problems in digital systems.

Experts point out that critical infrastructures may not be prepared for such a change. Therefore, the complete removal of the ‘now second’ is being considered an important option for technology companies and organizations responsible for timekeeping.

In the future, the Now-Second Application could come to the agenda.

If the proposal is accepted, time based on atomic clocks will be allowed to drift further from astronomical time based on Earth’s rotation. Thus, there will be no need to add a now second to clocks at regular intervals.

However, an unlimited increase in the difference between the two time systems is not anticipated. The proposal sets a limit that the gap will not exceed one hour. It is estimated that reaching that level could take thousands of years.

In such a case, future generations may have to consider a ‘now second’-like application to rebalance the difference between the two time systems.