Global timekeeping shift: Leap second may be replaced with leap hour

For more than fifty years, the world has been adding single seconds to its clocks in irregular bursts—a technical patch that keeps atomic time tethered to the actual rotation of the Earth. These leap seconds, inserted since 1972, have become an increasingly awkward solution to a fundamental problem: the planet spins at a variable rate, while the atomic clocks that govern global infrastructure tick with metronomic precision. Now, international timekeeping authorities are seriously considering abandoning this system altogether in favor of something radically different—a leap hour that would add time in much larger chunks, far less frequently, and with far fewer disruptions to the digital systems that depend on precise synchronization.

The leap second exists because of a mismatch between two ways of measuring time. Coordinated Universal Time, or UTC, is the global standard that keeps the world synchronized—it's what your phone uses, what financial markets use, what telecommunications networks use. But UTC is anchored to atomic clocks, which measure time with extraordinary precision and consistency. Earth's rotation, by contrast, is gradually slowing. A day today is not quite the same length as a day was decades ago. To prevent UTC from drifting away from solar time—from the actual position of the sun in the sky—timekeepers have periodically inserted an extra second. The first leap second came in 1972. Since then, they've been added irregularly, whenever the difference between atomic time and solar time accumulated enough to warrant correction.

The problem is that these insertions, though tiny, create real havoc in the digital world. Computer systems, financial trading platforms, telecommunications infrastructure, and satellite networks all depend on time synchronization down to fractions of a second. When a leap second is inserted, some systems handle it smoothly; others glitch, freeze, or produce errors. The disruptions are usually brief but can be costly. Financial markets have experienced trading anomalies. Social media platforms have gone down. GPS systems have faltered. Data centers have struggled to reconcile the sudden time shift across their networks. Each leap second is a small earthquake in the infrastructure that keeps the modern world running.

A leap hour would solve this problem by changing the scale and frequency of the correction. Instead of adding a single second at irregular intervals—sometimes years apart, sometimes just months—the new system would add a full hour, but only once every few thousand years. The mathematics work because the Earth's rotation is slowing at a predictable rate. By making the correction much larger but much rarer, the system would give digital infrastructure time to prepare, to update, to adapt. A leap hour would be a scheduled event, announced years in advance, rather than a surprise insertion that catches systems off guard. The disruption would still exist, but it would be singular, manageable, and foreseeable.

The shift would require international coordination of a scale that few technical decisions demand. The International Telecommunication Union, the body that sets global communications standards, would need to approve the change. National governments and their timekeeping authorities would need to align. The technology industry—from smartphone manufacturers to cloud computing providers to financial institutions—would need to prepare their systems. It is not a simple matter of flipping a switch. But the consensus among timekeeping experts is growing that the current system is becoming untenable, that the irregular leap second is a relic of an earlier era when computers were less central to global operations, and that a leap hour, though disruptive in its own way, is a more rational solution for a world that runs on synchronized digital time.

The conversation is still in its early stages. No decision has been made. But the direction is clear: the world is moving toward a timekeeping system that prioritizes the stability and predictability of digital infrastructure over the precise astronomical alignment that leap seconds have maintained. It is a choice that reflects how much has changed since 1972, when the first leap second was added and computers were still room-sized machines. Today, time synchronization is woven into nearly every system that matters. The leap second, once a clever solution, has become a liability. The leap hour, though it will require enormous coordination to implement, may be the more honest answer to the problem of keeping atomic time and solar time in step.