SUMMARYWorld timekeepers voted to eliminate the leap second, ending the practice of occasionally adding or subtracting a second to Coordinated Universal Time. The change allows UTC to drift farther from Earth’s rotation and defers any future correction for hundreds or thousands of years. The decision follows decades of debate over leap-second disruptions to computer systems and websites, including past outages and time-smearing workarounds used by companies like Google and Meta.
Timekeepers have officially voted to eliminate the leap second, allowing Coordinated Universal Time to drift as much as one hour from Earth's rotation before a correction is needed. The change ends decades of occasionally adding or subtracting seconds and replaces it with a hypothetical "leap hour" that likely wouldn't be necessary for hundreds or even thousands of years. Smithsonian Magazine reports: "It's kind of a philosophical discussion, because if a leap hour happens, it won't be for a very, very long time," Christian Bizouard, director of the IERS Earth Orientation Center in France, tells the Guardian's Ian Sample. "What we are doing is pushing back the decision."
The move caps off 30 years of debate, as the leap second has been highly controversial in the world of timekeeping. Leap seconds aren't nearly as smooth of a fix as leap years are, and they can cause computer and website issues. Reddit famously crashed when a leap second was added on June 30, 2012. It's "always been a problem," Judah Levine, a former researcher at the NIST's Time and Frequency Division, tells Scientific American's Emma Gometz.
Instead of adding the entire second all at once, companies such as Google and Meta add the extra time in smaller segments in a tactic called "smearing," according to the Conversation. It's not a simple task, however, and companies that employ smearing have long lobbied to get rid of the leap second. What's more, with Earth's recent spin acceleration, timekeepers around the world were facing the possibility of the world's first negative leap second, in which a second would be subtracted from UTC. This sparked fears, akin to those surrounding Y2K, that our modern technologies wouldn't be able to handle such a change.
"It's never happened before, and therefore the software for that has never been tested," Darryl Veitch, a researcher who leads the Timing Lab at the University of Technology Sydney, tells the Australian Broadcasting Corporation's Ellen Phiddian. But others argued that it wouldn't be much of a problem. The vote means that in the future, UTC will be allowed to diverge from astronomical time more than ever before.