World’s timekeepers upend how they adjust time to avoid catastrophic ‘negative second’
International delegates and governments have voted to abolish the leap second, with the change taking effect from May 2027. Timekeepers are replacing the practice of adding extra seconds to Coordinated Universal Time (UTC) with a leap hour system. This decision aims to prevent risks to computer systems and avoid the first negative leap second caused by an accelerating Earth. While the leap second is being phased out immediately, experts indicate a leap hour is unlikely to be necessary for thousands of years.
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- ✓ Governments voted to abolish the leap second and replace it with a leap hour.
- ✓ The practice of adding extra seconds to UTC will end from May 2027.
- ✓ Timekeepers cited risks to computer systems and the prospect of a negative leap second as reasons for the change.
- ✓ The first leap hour is not expected to occur for thousands of years.
What changed
Governments voted to scrap the leap second in favor of a leap hour starting May 2027.
Live updates
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Global Timekeepers Replace Leap Second with Leap Hour to Protect Computer Systems
International delegates and governments have voted to abolish the leap second, with the change taking effect from May 2027. Timekeepers are replacing the practice of adding extra seconds to Coordinated Universal Time (UTC) with a leap hour system. This decision aims to prevent risks to computer systems and avoid the first negative leap second caused by an accelerating Earth. While the leap second is being phased out immediately, experts indicate a leap hour is unlikely to be necessary for thousands of years.
Why it matters
Leap seconds were previously used to keep atomic clocks in sync with Earth's rotation. However, the accelerating speed of the planet created the possibility of a negative leap second, which threatened to cause catastrophic failures in digital infrastructure.
What is confirmed
- Governments voted to abolish the leap second and replace it with a leap hour.
- The practice of adding extra seconds to UTC will end from May 2027.
- Timekeepers cited risks to computer systems and the prospect of a negative leap second as reasons for the change.
- The first leap hour is not expected to occur for thousands of years.
What to watch next
- Implementation of the new timekeeping rules in May 2027
- Technical updates to big tech infrastructure to accommodate the change
confidence 100%Sources used for this update (9)
- The Guardian — How an accelerating Earth led experts to adopt the leap hour
- Al Jazeera — Clock ticking for leap second: Why timekeeping could change forever
- Smithsonian Magazine — It's Official: Timekeepers Have Gotten Rid of the Leap Second—and Introduced the Leap Hour Instead
- Nature — World’s timekeepers upend how they adjust time to avoid catastrophic ‘negative second’
- The Conversation — Experts have voted to stop adding extra seconds to clock time – the outcome favours big tech
- www.nature.com — World’s timekeepers upend how they adjust time to avoid ...
- www.euronews.com — World time to drop the leap second from May 2027 - Euronews
- www.theguardian.com — How an accelerating Earth led experts to adopt the leap hour
- www.hindustantimes.com — The leap second is being phased out. Why is the world ...
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