--- title: Rejoice, leap seconds are dead! | daily.dev description: UTC will never have another leap second added or removed, starting May 20, 2027. The CGPM passed Resolution 5, moving up the original 2035 deadline by 8 years.... canonical: https://daily.dev/posts/rejoice-leap-seconds-are-dead--fbyhu5exr twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Rejoice, leap seconds are dead! | daily.dev og:description: UTC will never have another leap second added or removed, starting May 20, 2027. The CGPM passed Resolution 5, moving up the original 2035 deadline by 8 years.... og:url: https://daily.dev/posts/rejoice-leap-seconds-are-dead--fbyhu5exr og:image: https://api.daily.dev/og/posts/fbyHu5eXR.png og:image:alt: Rejoice, leap seconds are dead! og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Rejoice, leap seconds are dead! **[Jeff Geerling](https://daily.dev/sources/jeffgeerling)** · 6 min read · 0 upvotes · 0 comments ## Summary UTC will never have another leap second added or removed, starting May 20, 2027. The CGPM passed Resolution 5, moving up the original 2035 deadline by 8 years. There was a 30% chance of needing a negative leap second before 2035, because Earth's rotation has been accelerating. There have been 27 positive leap seconds since 1972 but never a negative one. UTC will be locked 37 seconds ahead of TAI and may deviate from Earth's rotation by up to an hour. WWV radio time signals assume a sub-1-second offset, and astronomers and navigation systems have probably 5 to 10 years to solve the problem. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### When does UTC stop having leap seconds? UTC will never have another leap second added or removed starting May 20, 2027, following CGPM Resolution 5 passed at the 2026 General Conference on Weights and Measures. This moves up the original 2035 deadline set in 2022 by 8 years. UTC will stay permanently locked 37 seconds ahead of International Atomic Time (TAI). _Engineers maintaining time-sync code can track UTC and leap-second changes like this on daily.dev._ ### Why did the CGPM decide to eliminate leap seconds before the 2035 deadline? There was roughly a 30% chance a negative leap second would be needed before 2035, because Earth's rotation has been accelerating. Since 1972 there have been 27 positive leap seconds added but never one removed, so no system has ever handled a negative leap second, a scenario many feared could be worse than Y2K for untested time-handling code. _Anyone building resilient infrastructure follows edge-case failures like untested negative leap seconds on daily.dev._ ### What problems have companies like Meta, AWS, and Google had with leap seconds in their infrastructure? They spent significant money building 'time smearing' systems to gradually absorb positive leap seconds instead of inserting them abruptly, yet they still ran into problems despite that engineering effort. This history of costly workarounds and continued failures was part of the justification cited for abolishing leap seconds for UTC entirely starting in 2027. _Teams weighing the cost of clock-sync workarounds can follow infrastructure postmortems like this on daily.dev._ ## Similar posts on daily.dev - [The technical actions needed to ensure the continuity of UTC](https://daily.dev/posts/the-technical-actions-needed-to-ensure-the-continuity-of-utc-czabvh2py) · Hacker News · 0 upvotes · 0 comments - [Fwd: Bulletin C number 71](https://daily.dev/posts/fwd-bulletin-c-number-71-cirm6ctec) · Hacker News · 0 upvotes · 0 comments - [Ask HN: Are systems ready for the first negative leap second?](https://daily.dev/posts/ask-hn-are-systems-ready-for-the-first-negative-leap-second--whf0jsguw) · Hacker News · 0 upvotes · 0 comments --- Tags: [#distributed-systems](https://daily.dev/tags/distributed-systems) [View this post on daily.dev](https://daily.dev/posts/rejoice-leap-seconds-are-dead--fbyhu5exr) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Rejoice, leap seconds are dead!","url":"https://daily.dev/posts/rejoice-leap-seconds-are-dead--fbyhu5exr","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/rejoice-leap-seconds-are-dead--fbyhu5exr"},"datePublished":"2026-10-30T14:15:23.034Z","dateModified":"2026-10-30T14:15:51.804Z","description":"UTC will never have another leap second added or removed, starting May 20, 2027. 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This moves up the original 2035 deadline set in 2022 by 8 years. UTC will stay permanently locked 37 seconds ahead of International Atomic Time (TAI). Engineers maintaining time-sync code can track UTC and leap-second changes like this on daily.dev."}},{"@type":"Question","name":"Why did the CGPM decide to eliminate leap seconds before the 2035 deadline?","acceptedAnswer":{"@type":"Answer","text":"There was roughly a 30% chance a negative leap second would be needed before 2035, because Earth's rotation has been accelerating. Since 1972 there have been 27 positive leap seconds added but never one removed, so no system has ever handled a negative leap second, a scenario many feared could be worse than Y2K for untested time-handling code. Anyone building resilient infrastructure follows edge-case failures like untested negative leap seconds on daily.dev."}},{"@type":"Question","name":"What problems have companies like Meta, AWS, and Google had with leap seconds in their infrastructure?","acceptedAnswer":{"@type":"Answer","text":"They spent significant money building 'time smearing' systems to gradually absorb positive leap seconds instead of inserting them abruptly, yet they still ran into problems despite that engineering effort. This history of costly workarounds and continued failures was part of the justification cited for abolishing leap seconds for UTC entirely starting in 2027. Teams weighing the cost of clock-sync workarounds can follow infrastructure postmortems like this on daily.dev."}}]} ```