The Last Leap Second 15 October 2026 · Versailles
The world just retired
the leap second.
After 30 years of debate, the world's timekeepers voted to stop adding leap seconds — the tiny corrections that kept our clocks within 0.9 seconds of the spinning Earth. In 2027, UTC becomes continuous. Until then, can you keep time?
27 leap seconds since 1972
TAI − UTC 37 s
tolerance 0.9 s → 1 hour
continuous from 20 May 2027
Score0
Combo×1.0
Lives●●●
Sync—
the sweeping second hand
safe sync window
desync
Keyboard: Space to insert · P to pause · or tap anywhere on the dial.
Duty Officer · leap seconds inserted 0/27
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Duty Officer best
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Crisis best
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Times you reached 2027
What happened
One vote, and no clock will ever read 23:59:60 again
A leap second was a one-second adjustment added to Coordinated Universal Time (UTC) to keep clocks aligned with the irregular rotation of the Earth. It happened 27 times. On 15 October 2026, the General Conference on Weights and Measures (CGPM) in Versailles voted to stop.
Why it existed
Two clocks that disagree
Atomic clocks count a fixed SI second perfectly. The Earth does not. Its spin wobbles and slowly changes, so UTC was nudged by a leap second to stay within 0.9 s of UT1 — the time you read off the sky.
Why it ended
Computers hated the 61st second
A leap second makes time repeat itself. Reddit, LinkedIn and Qantas stumbled in 2012; Twitter, Netflix and a 61-minute halt at the New York Stock Exchange followed in 2015. Engineers began to fear a negative leap second far more.
What replaces it
The leap hour
From 20 May 2027 UTC is continuous. The allowed drift between Earth and clock grows from under a second to a full hour — a correction scientists expect will not be needed for more than 1,000 years.
“After 30 years of debates, we are ready.” Noël Dimarcq, president of the BIPM's Consultative Committee for Time and Frequency, moments before the vote · Scientific American
How the game works
You are the duty officer
Every second, Earth and the clock drift apart. When the drift reaches the danger line you must insert a leap second — at exactly the right moment. In Duty Officer mode you replay the 27 real leap seconds, from 1972 to 2016, and finish at the 2027 hand-over.
1 · Watch
Follow the hand
The gold hand is Earth's rotation. The teal window is the safe moment to act. The dial shows DUT1 — how far the sky sits from your clock.
2 · Strike
Press at the window
Tap the dial, press space, or hit the button as the hand crosses the glowing arc. Nail the centre for a PERFECT bonus and a bigger combo.
3 · Survive
Keep 0.9 seconds
Three desyncs and the clocks fall apart. Each leap second you place lights a notch on the ring. Place all 27 and you reach 2027.
Go deeper
Then spend a minute inside the machine
Time Lab
A live timekeeper's console
See UTC and TAI tick in real time, count down to the changeover, wind the clock forward to see the Sun drift, and walk all 27 leap seconds.
HistoryFrom sundials to caesium-133
How humanity measured the second — and the times a single second broke the internet.
QuizThe Timekeeper's Quiz
Fifteen questions on leap seconds, atomic clocks and DUT1. Get your verdict and share it.
AboutHow this was built
The story behind the site, how the game models the real problem, and every source used.