BIPM's 69 member states vote this week on retiring the leap second

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.