tech · science
the world votes to stop adding leap seconds to its clocks
from may 2027, the clock your phone and the grid run on can drift up to an hour from the spinning earth, so nobody ever has to delete a second.
- 27, leap seconds since 1972
- 0.9S, drift allowed today
- 1 HOUR, drift allowed from 2027
since 1972 the world’s official clock has been nudged 27 times, each time by one extra second, so that it never strays more than 0.9 seconds from the time told by the earth’s rotation. last week the general conference on weights and measures, the body that keeps the metre and the kilogram, voted to stop. under its resolution 5, from 20 may 2027 utccoordinated universal time, the atomic clock time the whole world sets its clocks by. may wander up to 3,600 seconds from ut1time worked out from how far the earth has actually turned. it wobbles, because the planet’s spin speeds up and slows down., which the bipm says is enough to need no correction for several centuries.
the reason is a second nobody has ever had to remove. the earth has lately been spinning a little faster, and a 2025 workshop put the odds of a negative leap second at about 30 percent by 2035. software expects an extra second, not a missing one. the resolution says getting ready for one would cost about as much as the y2k fixes, and that cheap connected gadgets, smart grids and phone networks are exactly where a stray second causes trouble. big providers already handle leap seconds in their own different ways, so their clocks disagree with each other.
the link to the sky is not cut. ut1 will still be measured and the gap published, setnam shemar of the uk’s national physical laboratory told the register. local time already sits an hour or more away from the sun in plenty of places thanks to time zones and summer time, which the resolution points out too.
how much slack the clock now has
use the arrow keys to step bigger or smaller
today’s limit: 0.9 s. the most utc may differ from earth time before a leap second goes in.
- today’s limit: 0.9 s. the most utc may differ from earth time before a leap second goes in.
- one leap second: 1 s. the step a clock has had to take, 27 times so far.
- every leap second: 27 s. all the seconds added since 1972, together.
- the new limit: 3,600 s. one hour, enough for centuries of drift.
pick one
every leap second so far has added time. how many have ever taken a second away?
next: continuous utc starts on 20 may 2027. equipment that cannot be replaced in time gets until 2040 at the latest under the itu’s rules, so watch for the last systems still expecting a leap second.