A single extra second inserted into official clocks has caused servers to seize up, delayed commercial flights, and knocked major websites offline. To protect vulnerable computer networks from technical chaos, international timekeepers have voted to scrap the troublesome leap second in favor of a much larger adjustment: the leap hour. Delegates from 69 countries approved the historic change at a conference in Versailles, France, ending three decades of debate over how the world synchronizes its clocks.
Since 1972, officials have added 27 leap seconds to align Coordinated Universal Time (UTC)—measured by ultra-precise atomic clocks—with the Earth's natural rotation. While atomic time relies on steady vibrations of caesium atoms, the planet's spin is less predictable, influenced by its molten core, ocean movements, and atmospheric winds. When an extra second created a 61-second minute in 2012, some operating systems failed to cope. The glitch temporarily brought down platforms like Reddit and LinkedIn, while also causing delays for Qantas flights. Telecommunications networks and electricity grids also face severe disruption if software updates apply leap seconds at different times.
The urgency to change the system increased because Earth's rotation has recently accelerated, creating a 30 percent probability of needing a "negative leap second"—removing a second from the clock—within the next decade. Dr. Setnam Shemar, a principal scientist at the UK's National Physical Laboratory, warned that dropping a second carries even greater risks because software systems worldwide have never been tested on 59-second minutes. Testing and upgrading every interconnected system would cost companies an enormous fortune.
Starting next year, official time will instead be permitted to drift up to an hour from astronomical time before any correction is required. Scientists calculate that such a difference will not accumulate for thousands of years. Dr. Christian Bizouard, director of the Paris-based IERS Earth Orientation Centre, remarked that the vote effectively passes the problem to people far in the future. When a leap hour is eventually needed, experts expect society to handle it smoothly, much like the familiar one-hour shift of daylight saving time.