From WIRED · Brian Kahn · · 2m
The leap second is officially dead
After 50 years, the International Bureau of Weights and Measurements will stop adding leap seconds in May 2027, ending a three-decade debate over a timekeeping adjustment that has caused major tech headaches.
In brief
After 50 years, the International Bureau of Weights and Measurements will stop adding leap seconds in May 2027, ending a three-decade debate over a timekeeping adjustment that has caused major tech headaches. The International Bureau of Weights and Measurements will abolish the leap second in May 2027, ending a…
The leap second dies in 2027
The International Bureau of Weights and Measurements announced Thursday that it will stop issuing leap seconds in May 2027, ending a practice that has been added 32 times since 1972.
Why leap seconds exist
The world implemented the leap second in 1972 to keep atomic-clock-driven Coordinated Universal Time aligned with astronomically kept Universal Time, as Earth's rotation is slowing due to tidal friction.
Leap seconds break technology
Leap seconds have caused major problems for tech systems relying on Coordinated Universal Time. The airline Qantas saw its booking system fail due to a leap second in 2012.
“the airline Qantas, for example, saw its booking system borked by a leap second in 2012”
The negative leap second threat
Earth has picked up rotational speed in recent years due to climate change, raising the odds of needing a negative leap second. A 2024 Nature study suggested one might be required as soon as 2029.
Negative leap seconds are untested
Judah Levine of the US National Institute of Standards and Technology says there are continuing problems with positive leap seconds after 50 years, and negative ones would be much more serious because their effects have…
“There are continuing problems with positive leap seconds even after 50 years, and the concern was that the negative leap second would be much more serious because its effects had never been tested”
Why May 20, 2027
BIPM director Patrizia Tavella says the group chose May 20, 2027 because it is the anniversary of the 1875 signing of the Metre Convention, which created BIPM, and also marks Metrology Day.
Life gets simpler without leap seconds
Tavella says the nice fact is that systems will have nothing to do and can just continue to accumulate seconds and normal minutes of 60 seconds. Levine agrees that life will have one less hassle.
“The nice fact is that we have nothing to do! Just continue to accumulate second[s] and 'normal' minutes of 60 seconds.”
A leap hour waits in the future
BIPM agreed to create a leap hour to handle the ongoing drift between atomic time and astronomical time. Given that there are 3,600 seconds in an hour, a leap hour is millennia away.
The main idea
The International Bureau of Weights and Measurements will abolish the leap second in May 2027, ending a practice that has caused repeated technology failures and risked introducing a dangerous negative leap second.
