The Last Leap Second About
A game about the second the world just retired
On 15 October 2026 the 28th General Conference on Weights and Measures voted to stop inserting leap seconds into Coordinated Universal Time. This site is a playable response to that news: a precision timing game, plus the instruments and history to understand what actually changed.
How the game models the real problem
Timekeeping is a tug-of-war between two clocks. Atomic time ticks a fixed SI second forever. Earth's rotation wanders and slowly changes, so the sky and the clock pull apart. For fifty years the world closed the gap with a leap second: a one-second step that kept the difference — called DUT1 — inside ±0.9 seconds.
In the game, the gold hand is Earth's rotation and the teal window is the moment a leap second must be inserted. The readout in the hub shows DUT1 drifting from +0.1 s toward −0.9 s; hit the window and the drift snaps back, exactly as a positive leap second resets the real thing. Each of the 27 notches on the ring stands for one of the 27 leap seconds actually inserted between 1972 and 2016 — the same dates you can browse in the Time Lab.
It is a game, not a simulation. Real Earth rotation is unpredictable, and the numbers here are tuned for play. But the tension it dramatises — act at the right moment, or the world's clocks drift out of step — is the real one that engineers spent thirty years trying to delete.
What's inside
Built to be explored in a sitting
The game
Three modes — Practice, Duty Officer (all 27 leap seconds, 1972 → 2027) and Crisis (endless). Combos, per-centre PERFECT bonuses, three lives, notch ring, and a shareable result card you can download.
Time Lab
Live UTC and TAI readouts, a countdown to 20 May 2027, a drift simulator that winds the clock toward the year 5000, a "your life in leap seconds" calculator, and the clickable record of all 27 leaps.
History
A short history of the second and a gallery of real incidents — Reddit, Qantas, the NYSE — where a single leap second knocked systems offline.
The quiz
Fifteen sourced questions with explanations, a verdict, and a shareable score. Your best score is kept in your browser only.
Sources
All facts, figures and quotes on this site were taken from the following reporting and reference material, read on 16 October 2026.
| Source | Used for |
|---|---|
| Wikipedia — Leap second | 27 leap seconds and their dates, TAI − UTC = 37 s, the 0.9 s rule, the 1967 caesium definition, the "rubber second" era, leap smear, GPS bugs, the 2012/2015 incidents |
| Scientific American — 15 Oct 2026 | The vote and its "leap hour", the Dimarcq and Stamatakos quotes, the "mini Y2K" framing, the 1,000-year expectation |
| Al Jazeera — 15 Oct 2026 | 69 member states, 37 seconds, the Meta quote, the 2012/2015 outages, 54 seconds of drift by 2100, the Russia/GLONASS objection, the 20 May 2027 date |
| BIPM — Resolution 5, 28th CGPM (2026) | The formal resolution on the technical actions needed to ensure the continuity of UTC |
| NIST / USNO time services | Background on UTC, UT1 and leap-second announcements (IERS Bulletin C) |
The live clocks read your own device time. TAI is shown as UTC + 37 s, which is exact while leap seconds remain. DUT1 and the drift simulator are clearly-labelled illustrations, not official values — for those, see the IERS.
Credits & notes
All prose, code, games, data and artwork are original and were made for this page. Typefaces are Space Grotesk and IBM Plex Mono, served by Google Fonts. The site is pure static HTML, CSS and JavaScript with no backend, no build step, no API keys and no trackers; progress is saved only in your browser's local storage.
This is a playful, non-official tribute and must not be used as a time reference. For the official story, follow the sources above.