--- title: How an HTTP header caused time.gov to skew from UTC description: A deep dive into why time.gov displayed inaccurate clock offsets. The root cause was the HTTP `Connection: close` header, which forced browsers to create a new... canonical: https://daily.dev/posts/how-an-http-header-caused-time-gov-to-skew-from-utc-bx8wwerln twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: How an HTTP header caused time.gov to skew from UTC | daily.dev og:description: A deep dive into why time.gov displayed inaccurate clock offsets. The root cause was the HTTP `Connection: close` header, which forced browsers to create a new... og:url: https://daily.dev/posts/how-an-http-header-caused-time-gov-to-skew-from-utc-bx8wwerln og:image: https://api.daily.dev/og/posts/bx8wWErLn.png og:image:alt: How an HTTP header caused time.gov to skew from UTC 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. # How an HTTP header caused time.gov to skew from UTC **[Lobsters](https://daily.dev/sources/lobsters)** · 9 min read · 3 upvotes · 1 comments ## Summary A deep dive into why time.gov displayed inaccurate clock offsets. The root cause was the HTTP `Connection: close` header, which forced browsers to create a new TCP+TLS connection for every request. The JavaScript timing code assumed a single network round-trip (like NTP), but actually measured three, introducing a full round-trip worth of error. NIST fixed the issue around April 24th by switching to `keep-alive`. The author also proposes using the `PerformanceResourceTiming` API for more precise measurement of just the HTTP layer, and provides a client-side patch demonstrating the improvement. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Server Timing: Measure And Track Backend Performance](https://daily.dev/posts/server-timing-measure-and-track-backend-performance-m1j2axzux) · DebugBear · 6 upvotes · 2 comments - [Fixing the URL params performance penalty](https://daily.dev/posts/fixing-the-url-params-performance-penalty-61quehkfp) · Web Performance Calendar · 1 upvotes · 0 comments - [HTTP1 vs HTTP2 vs HTTP3](https://daily.dev/posts/http1-vs-http2-vs-http3-wbpqmgwlo) · System Design Newsletter · 170 upvotes · 5 comments - [Help desk read useless script, so techies made their own fix](https://daily.dev/posts/help-desk-read-useless-script-so-techies-made-their-own-fix-2feveop70) · The Register · 0 upvotes · 0 comments - [HTTP/2 and HTTP/3: what changed and why it matters](https://daily.dev/posts/http-2-and-http-3-what-changed-and-why-it-matters-kxd7rny7x) · Flavio Copes · 1 upvotes · 0 comments --- Tags: [#javascript](https://daily.dev/tags/javascript) [View this post on daily.dev](https://daily.dev/posts/how-an-http-header-caused-time-gov-to-skew-from-utc-bx8wwerln) ```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":"How an HTTP header caused time.gov to skew from UTC","url":"https://daily.dev/posts/how-an-http-header-caused-time-gov-to-skew-from-utc-bx8wwerln","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/how-an-http-header-caused-time-gov-to-skew-from-utc-bx8wwerln"},"datePublished":"2026-05-07T00:26:18.667Z","dateModified":"2026-05-07T00:26:46.546Z","description":"A deep dive into why time.gov displayed inaccurate clock offsets. 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