The Last Leap Second Time Lab
The clock, the sky, and the second they could no longer agree on
Four live instruments. Watch the two official timescales tick apart in real time, count down to the moment UTC becomes continuous, wind the calendar forward to see how far the Sun would slip — then walk every leap second ever inserted.
Live console
The two timescales
UTC — Coordinated Universal Time--:--:--
TAI — International Atomic Time--:--:--
TAI − UTC (fixed since 2016)37 s
DUT1 · UT1 − UTC (modelled)+0.00 s
—
UTC and TAI are shown from your device clock; TAI is UTC + 37 s. DUT1 is a smooth illustrative model (real values come from IERS Bulletin D), shown so you can watch the sky and the clock breathe apart.
Countdown
Until UTC becomes continuous
The CGPM vote takes effect on 20 May 2027 — World Metrology Day. After that date no new leap seconds will be added.
Days0
Hours00
Minutes00
Seconds00
The allowed gap between Earth time (UT1) and clock time (UTC) rises from ±0.9 s to 3,600 s — one whole hour. Scientists expect a "leap hour" correction will not be needed for more than 1,000 years.
Drift simulator
What if we had never corrected the clocks?
Atomic seconds tick forever at the same rate. Earth does not. Slide into the future to see how far "clock noon" would wander from the real noon — the very reason leap seconds, and now a leap hour, exist.
20262500300040005000
Clock ahead of the Sun by0 seconds
A leap second would have been needed—
Clock noon is still close to solar noon.
Rough model, anchored to the reported figure of about 54 seconds of drift by the year 2100 (Al Jazeera) and the expectation that a one-hour correction is more than 1,000 years away (Scientific American). Long-run drift accelerates, so this is an illustration of scale, not a forecast.
Your life in leap seconds
How many of the 27 landed during your lifetime?
The full record
Every leap second ever inserted
Twenty-seven one-second decisions, from the very first on 30 June 1972 to the last on 31 December 2016. Click any notch or row for the detail.