To balance out a very gradual slowing of the Earth’s rotation, scientists are adding an extra second to the day on Tuesday.

The so-called leap second is imperceptible to humans — there have been 25, most of them uneventful, since 1972 — but lately it has been known to throw many of the systems we use out of sync.

For some people in science and technology, the practice of adding extra seconds to the day with relatively little advanced warning is more disruptive than helpful. At its most harmless, the practice is criticized as anachronistic. (If humans can’t tell the difference and it will be thousands of years until a shift is noticed, is it really necessary? a writer at Quartz argued.) At its worst, the leap second can disrupt entire computer systems that were not made to account for flexibility in time.