BIPM's 69 member states vote this week on retiring the leap second
BIPM member states vote this week on ending the leap second, in a resolution that would take effect in May 2027. A yes vote lets UTC drift from Earth's rotation. CNN reported the change would touch systems that telecoms, power grids and computers rely on.
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What happened
- Passing needs a majority of votes, BIPM time department director Patricia Tavella said.
- Leap seconds have been added 27 times since 1972, most recently at the end of 2016.
- At its 2022 meeting the body backed a resolution calling for a plan to phase out leap seconds by 2035 at the latest.
- Earth has been spinning faster since about 2020, so the next leap second might have to be negative, according to ABC.
Why it matters
- What doesn't add up contradiction Wouters expects a negative second to be easier on software than a positive one. Veitch says the code for it has never been tested. The two experts disagree on the case that forced the faster timetable.
- Who's exposed exposure A failed vote leaves the negative leap second on the table. If Earth keeps speeding up, it would run on software that Veitch says has never been tested.
- What it limits constraint Passing takes a majority of votes, so no single objector can block it, including Russia, which cited GLONASS in 2022.
Next story · Science · yesterday
Delegates in Versailles vote to end the leap second from May 2027Confirmed7 publishers
Leap seconds are irregular. Unlike time zones or daylight saving, they are scheduled only six months ahead [7]. Darryl Veitch, a computer networking researcher at the University of Technology Sydney, said they broke some software's assumptions about time, such as that it only moves forwards and that a minute has 60 seconds [8]. Michael Wouters, who leads time standards at Australia's National Measurement Institute, said people "forgot about this problem, and they wrote software that then crashed when time went backwards" [9].
The outages are on record. According to CNN's account, carried by mezha.net, the extra second in 2012 caused failures at Reddit and LinkedIn and took down Qantas's booking system [10]. When a second was added at the end of 2016, Cloudflare customers briefly saw failures or delays because the company's servers did not handle it properly [11]. Meta and other technology companies urged abolition, CNN reported [12].
The negative second is where the two Australian experts part. Wouters said it was less likely to cause problems because it makes time jump forwards [20]. Veitch was not so sure. "It's never happened before, and therefore the software for that has never been tested," he said [21]. Wouters described the faster timetable this way: "It's being cautious about an unusual event that's prompting the accelerated timetable" [15]. In our view Veitch has the firmer ground, because an untested path is an unknown whichever way the clock jumps.
Handling is already uneven across satellite systems. Tavella said Russia's 2022 opposition was tied to GLONASS, its navigation system, which accounts for leap seconds, unlike the US GPS and the European Galileo [16]. The UK objected over Greenwich's historical role in timekeeping and later changed its position [17].
A May 2027 effective date would land roughly eight years before the 2035 limit set in 2022 [19]. ABC reports that, if the vote succeeds, the replacement is to ask people centuries from now to observe a "leap hour" [13]. Neither report describes how the change would be applied in practice. If it passes, telecom, grid and computer operators will have to decide what their clock code does once UTC stops taking leap seconds.
What to watch
- The Versailles tally: whether a majority backs the resolution with its May 2027 effective date.
- How Russia votes, given that it tied its 2022 opposition to GLONASS counting leap seconds.
- Whether the BIPM publishes the replacement scheme, including the "leap hour" ABC describes, and any guidance for infrastructure operators.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence62
- Adoption
- Not scored
- Hype gap+8
- Incentives40
- Confidence60
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
The BIPM, an intergovernmental body that sets measurement standards, has 69 member states, which meet this week in Versailles near Paris to consider a resolution that would take effect in May 2027.
- [2]
Delegates meet near Versailles later this week to decide whether to abandon the leap second for good.
- [3]
Supporting the proposal requires a majority of votes, said BIPM time department director Patricia Tavella.
- [4]
Since their introduction in 1972, leap seconds have been added 27 times, most recently at the end of 2016.
- [5]
At the 2022 meeting, member states backed a resolution calling for a plan to phase out leap seconds by 2035 at the latest.
- [6]
The proposal to abolish leap seconds would eventually let official time drift away from the Earth's rotation.
- [7]
Unlike time zones or daylight saving, leap seconds are irregular and scheduled only six months in advance.
- [8]
Darryl Veitch, a computer networking researcher at the University of Technology Sydney, said leap seconds broke some software's assumptions about time, such as that it only moved forwards and there were 60 seconds in a minute.
- [9]
Michael Wouters, Australia's National Measurement Institute leader of time standards, said people "forgot about this problem, and they wrote software that then crashed when time went backwards".
- [10]
In 2012 an extra second caused outages at Reddit and LinkedIn and took down Qantas's booking system.
- [11]
When a leap second was added at the end of 2016, Cloudflare customers briefly saw failures or delays because the company's servers could not handle it properly.
- [12]
Meta and other technology companies urged that leap seconds be abolished, describing them as a serious source of problems.
- [13]
If the vote succeeds, the replacement will ask people centuries in the future to observe a "leap hour".
- [14]
Since about 2020 Earth has sped up, which means the next leap second might need to be negative.
- [15]
"It's being cautious about an unusual event that's prompting the accelerated timetable," Dr Wouters said.
- [16]
Tavella said Russia's 2022 position was tied to GLONASS, its satellite navigation system, which accounts for leap seconds unlike the American GPS and European Galileo.
- [17]
The UK objected to abolition because of Greenwich's historical role in measuring time, but later changed its position, Tavella said.
- [18]
The change would affect systems used by critical infrastructure, including telecommunications, power grids and computers.
- [19]
A May 2027 effective date is roughly eight years ahead of the 2035 outer limit set in 2022.
- [20]
Wouters said a negative leap second was less likely to cause problems because it involves time jumping forwards.
- [21]
"It's never happened before, and therefore the software for that has never been tested," Professor Veitch said of a negative leap second.
Sources
2 independent publishers whose own reporting we read for this story.
- abc.net.auWorld's timekeepers to vote on ditching leap second - ABC News
1 article · October 11, 2026
- mezha.netМіжнародні хранителі часу розглянуть можливість скасування високосної секунди
1 article · October 13, 2026
Topics and entities
Topics
- Critical infrastructure software