Leap Seconds Could End in 2027 as BIPM Plans New Timekeeping Rules

The problem with positive leap seconds has persisted for 50 years. Experts also warned that negative leap seconds could create even more serious issues because their effects had never been tested, according to Levine.

Why BIPM Is Ending Leap Seconds

Patrizia Tavera, director of the BIPM’s time division, acknowledged these concerns in an email to WIRED. “The possibility of a negative leap second convinced us [to] set an application date of 2027,” she wrote. She added that industry standards bodies had conducted tests that “showed several failures with negative jumps.”

The organization plans to implement the change on May 20, 2027. The date marks the anniversary of the 1875 signing of the Meter Convention and the founding of the BIPM. It is also World Metrology Day, making it a fitting occasion to mark a major change in how global time is measured.

What the End of Leap Seconds Means

Ending leap seconds will simplify timekeeping for computer systems, networks and other technologies that depend on Coordinated Universal Time (UTC). “The good fact is that we have nothing to do!” Tavera said. “Just keep adding seconds.” A standard minute will continue to contain 60 seconds.

Levine agreed, writing that the change “will be one less hassle in your life.”

Atomic Time and Astronomical Time Will Still Diverge

Removing leap seconds will not eliminate the ongoing difference between atomic time and astronomical time. For that reason, the BIPM also agreed to create a leap time.

However, leap time is thousands of years away because it would take many leap seconds for the difference to accumulate significantly. After all, there are 3,600 seconds in an hour.

“We haven’t talked about leap time yet,” Tavera said. “If your system relies on UTC, you don’t need to do anything. If you rely on UT1, your system must be able to use the information UT1-UTC when, in the future, it becomes greater than one second.”

In other words, ending leap seconds is unlikely to affect everyday life. The larger consequences will be left to future generations and the systems they develop to account for the growing difference between atomic and astronomical time.