Time is a-changin’: say goodbye to the leap second

An important change will soon be made to global timekeeping that aims to prevent potential infrastructure failures akin to the Y2K bug scare. On Thursday, the International Bureau of Weights and Measures (BIPM) voted to scrap the leap second, an ad hoc time adjustment that’s occasionally added so tracked time standards mirror the Earth’s real (and inconsistent) rotation.

BIPM members previously agreed in 2022 to cease using leap seconds on or before 2035, but this is now being expedited to take effect on May 20th next year, aligning with World Metrology Day. There’s an unprecedented reason for its retirement being brought forward: changes to the Earth’s rotation may soon require timekeepers to subtract time instead of adding it in order to keep astronomical time in line with atomic time. This has never been attempted before, and there are concerns that doing so could wreak havoc on critical infrastructure that relies on time synchronization.

Those fears aren’t unfounded given Foursquare, Reddit, LinkedIn, Yelp, and many other tech platforms have suffered outages in the past when leap seconds have been added. Companies including Meta, Google, Microsoft, and Amazon have all supported efforts to scrap the system. Following the BIPM vote, timekeepers will instead switch to using “leap hours,” allowing atomic and astronomical time to gradually drift apart until an entire hour needs to be added — which isn’t expected to happen for around 3,000 years.