The Earth has been spinning unusually quick just lately. Final yr on July 4, our planet set a document by finishing a full spin 1.66 milliseconds (0.00166 seconds) sooner than common, in keeping with timeanddate.com. One yr later, on July 10, 2025, Earth accomplished a every day rotation that scientists estimate was 1.36 milliseconds sooner than common, giving us one other significantly brief day. Different shorter (however ever-so-slightly longer) days occurred on July 9 and July 22, though the precise margins have but to be confirmed.
Shedding a pair milliseconds could seem insignificant to most of us—maybe justifiably so. However tiny error margins in time can mess up methods that rely on extraordinarily exact calculations, reminiscent of high-speed communication networks, GPS, or banking methods. As such, scientific timekeepers use extremely subtle atomic clocks to set the usual through the Coordinated Common Time (UTC). However with the latest acceleration in Earth’s rotation, the necessity for a “destructive” leap second has re-emerged amongst some timekeeping consultants.
Scientists repeatedly apply a leap second to preserve UTC synchronized with astronomical time, which they base on Earth’s rotation. A full day on Earth—the time it takes our planet to finish one full rotation on its axis—lasts for 86,400 seconds. However elements such because the Solar’s place, the Moon’s orbit, and Earth’s gravitational area affect how rapidly the Earth completes its every day cycle. In consequence, Earth’s rotation finally ends up being irregular, and slight variations between UTC and astronomical time can add up in the long term, inflicting a mismatch between the 2.
Leap seconds right for this deviation. By the identical logic, a destructive leap second would subtract an additional second from UTC to account for the milliseconds we’re shedding from Earth’s sooner rotation. Now, this will likely appear completely affordable, however not all scientists agree. Actually, some scientists discovered the leap second so problematic that, in 2020, a world group of consultants voted to section out the apply by 2035.
As computing networks grew to become extra globally interconnected, the leap second started to trigger “failures and anomalies in computing methods,” Patrizia Tavella, director of the Worldwide Bureau of Weights and Measures’ time division, advised Stay Science in a 2022 interview. Furthermore, international locations account for leap seconds in numerous methods, inflicting main problems for airways scheduling worldwide flights, she stated.
Critics of the proposed destructive leap second cite comparable considerations. To be clear, no formal establishment or physique is presently advocating for the destructive leap second. However ought to that occur, squeezing within the destructive leap second to our timekeeping system shall be troublesome given the more and more interconnected nature of our society, Darryl Veitch, a pc networking skilled, defined to Stay Science in a latest interview.
“There are persevering with issues with the insertion of optimistic leap seconds even after 50 years,” Judah Levine, a physicist on the College of Colorado, advised Stay Science. “And this will increase the considerations in regards to the errors and issues of a destructive leap second.”
It appears unlikely, subsequently, that scientists will really undertake the destructive leap second, particularly since they’ve already determined to retire the optimistic leap second. However given Earth’s latest shorter every day spins, astronomical time would possibly ultimately fall behind UTC, forcing the necessity for destructive leap seconds. Levine places the chance of this occurring at 30% within the subsequent decade or so, though final yr, Duncan Carr Agnew, an oceanographer on the Scripps Establishment of Oceanography, argued in a paper from final yr that this might happen as early as 2029. Nevertheless, Veitch additionally believes our planet would possibly decelerate quickly, which might be in step with longer-term tendencies on document.
However we’ll simply should see—and you’ll, too! Timekeepers estimate that our subsequent “brief” day will fall on August 5.
