International timekeeping authorities are preparing for a major overhaul of how the world measures time, with discussions underway to redefine the second and to replace the leap second with a leap hour. The changes were debated at the General Conference on Weights and Measures (CGPM), which brings together scientists, diplomats, and timekeepers from around the globe.
According to reports from The Economist and Scientific American, the conference has called for a new definition of the second to be prepared for consideration at its next meeting in 2030. The move comes as several advanced atomic clocks, including those based on strontium, are competing to become the new standard. However, no consensus has yet been reached on which atomic species will ultimately define the second.
The current definition of the second, which has been in place for nearly 60 years, is based on 9,192,631,770 cycles of microwave radiation from the caesium-133 atom. This method has provided a highly stable and precise measure of time, but recent advances in optical clock technology promise even greater accuracy and reliability.
Among the contenders for the new standard is the strontium optical clock, which uses the vibrations of strontium atoms exposed to laser light. Optical clocks operate at much higher frequencies than microwave-based caesium clocks, allowing for more precise timekeeping. Several other atomic species are also being considered, but the conference has yet to agree on which offers the best combination of stability, accuracy, and practicality for international adoption.
In a separate but related decision, the CGPM has voted to end the use of the leap second, a periodic adjustment that has been used to keep Coordinated Universal Time (UTC) within one second of Universal Time (UT1), which is based on Earth’s rotation. Instead, the leap second will be replaced by a leap hour, which will only be added much less frequently, allowing the difference between UT1 and UTC to grow to as much as one hour before an adjustment is made. This change is set to take effect in May 2027, according to Scientific American.
The leap second has long been a source of technical challenges for digital systems and global infrastructure, as its unpredictable insertion can disrupt software and networks. The move to a leap hour is expected to simplify timekeeping and reduce the risk of disruptions, particularly as Earth’s rotation has become less predictable in recent years.
Experts say these changes reflect both technological progress and the growing complexity of global timekeeping requirements. The adoption of a new atomic definition for the second is expected to further improve the precision of technologies that rely on accurate time, including navigation, telecommunications, and scientific research.
The final decision on the new definition of the second is expected at the 2030 CGPM meeting. Until then, scientists will continue to evaluate the competing atomic clocks and prepare for the transition to a new era of time measurement.
The image accompanying this article is an AI-generated illustrative depiction inspired by the actual scene of the event.
