Earth Rotation Drift Clock Screensaver
The Earth Rotation Drift Clock shows the live UT1−UTC offset — how far Earth's actual rotation has drifted from atomic time — from the IERS's daily earth-rotation series, with the drift per day, a chart including the official two-week prediction, and a gauge of the ±0.9 s leap-second band. It's free, needs an internet connection, and ESC exits.
How the Earth Rotation Drift Clock screensaver works
The pipeline pulls the IERS rapid-service series (USNO finals.daily) into content/ut1drift.json — about three months of real daily UT1−UTC values plus the IERS ~two-week prediction.
The hero readout interpolates between the daily points to the current moment, always signed and shown to four decimals of a second.
The chart draws measured days as a solid line and the prediction tail dashed and dimmer, with today marked; the drift-per-day figure says how much longer or shorter than 86,400 s the day is running.
A gauge places the current offset inside the ±0.9 s band — when |UT1−UTC| threatens that limit, the IERS schedules a leap second.
A worked example
Right now it reads UT1 − UTC = +0.0115 s, drifting about −0.019 ms per day — each day running a whisker longer than 86,400 atomic seconds — with the marker sitting at 1.3% of the leap-second band. Run it next to Leap Second Watch in Multi-view: the archive of past leap seconds beside the live dial that decides the next one.
Settings & tips
- Leap-second gauge — hides the ±0.9 s band strip if you'd rather give the chart the full height, e.g. in short, wide Multi-view cells.
Frequently asked questions
- Is this real, live data?
- Yes. The values are the IERS rapid-service earth-orientation measurements (published daily as finals.daily), fetched by the site's pipeline. The on-screen value is interpolated between daily points, and the badge shows when the feed is connected.
- Why does Earth's rotation speed wobble?
- Angular momentum is constantly traded between the solid Earth, its molten core, the oceans and the atmosphere — tides, winds, ice and even large earthquakes all nudge the day's length by milliseconds. That's why UT1 drifts against uniform atomic time.
- What happens if the offset reaches ±0.9 seconds?
- The IERS inserts a leap second into UTC to pull civil time back toward Earth's rotation — that's the band the gauge shows. With Earth spinning unusually fast lately, timekeepers are seriously debating the first-ever negative leap second, a minute with only 59 seconds.
- How is this different from the Leap Second Watch saver?
- Leap Second Watch is the historical archive — every leap second since 1972. This is the live instrument: the current UT1−UTC offset, its daily drift and the prediction of where it's heading.
- Is it free, and does it need a key?
- Yes, free — no key, no download, in your browser. It needs an internet connection to read the pipeline feed; ESC exits at any time.