At its 2025 General Conference on Weights and Measures, held in Versailles, France, the International Bureau of Weights and Measures (BIPM) passed a resolution by majority vote to phase out the practice of inserting leap seconds into Coordinated Universal Time. The adjustment is slated to take effect on 20 May 2027 at 12:00:00 UTC, a date that falls on World Metrology Day.
Under the updated framework, the precise atomic timekeeping that underpins satellites, navigation networks, financial systems, and internet-connected devices across the globe will be free to operate independently of the planet's uneven rotation. Under the new arrangement, the gap between TAI-derived UTC and the slower Earth-rotation measure known as UT1 is free to widen without correction, potentially accumulating a discrepancy of around one hour — roughly 3,600 seconds — across an extended period.
Adopted in 1972, the leap-second system was designed to bring atomic timekeeping — which defines the duration of a second — into alignment with the planet's actual rotational period as measured through physical observation. In the period that followed, 27 of those additional seconds were incorporated into official timekeeping. Aligning ordinary timekeepers with the natural arc of daylight was understood to be a prerequisite for holding civil time, navigation, and astronomical observation in mutual agreement.
Mounting complications tied to the one-second jump rule have made the standard harder to sustain over time. Each adjustment to the global timekeeping standard — whether a second gained or lost — has historically introduced operational problems for the computer infrastructure that depends on precise timestamps, including data centres, cloud platforms, high-frequency trading systems, and air-traffic control networks.
When a leap second was inserted in 2012, the adjustment triggered roughly 40 minutes of downtime at Reddit, a brief interruption to LinkedIn's service, and knock-on delays across Qantas flights. Cloudflare's infrastructure ran into trouble handling the extra second inserted into the calendar that year, leaving many of the platform's users without reliable service.
Under the BIPM resolution, clocks and calendars retain a thread of connection to Earth's rotation rather than breaking from it entirely. What this change does, in effect, is release the atomic timekeeping standard from any requirement to insert abrupt one-second corrections.
Across centuries, timekeeping instruments such as clocks and sundials will accumulate drift of roughly an hour, yet that divergence builds so gradually that operations ranging from space launches to electrical grid management are not expected to require any manual adjustments within any near-term planning horizon. Most timing-dependent infrastructure — including networks built around Network Time Protocol (NTP) or Precision Time Protocol (PTP) — carries built-in tolerance for small astronomical fluctuations, according to technical assessments.
Setnam Shemar, principal scientist at the National Physical Laboratory, characterised the move as a natural progression, noting that while atomic timekeeping now delivers extraordinary consistency, it grows ever more misaligned with the Earth's irregular rotation — a tension that has exposed precision-dependent technologies to operational vulnerabilities through the continued use of leap seconds.
Tolerating incremental change over time removes the pressure to deploy emergency fixes or last-minute patches. The connection between global timekeeping and the planet's rotation will be maintained, though with greater flexibility than before — atomic clocks will govern computer networks worldwide, while astronomers continue tracking the Sun and stars, with the two systems permitted to drift apart only within bounds considered acceptable for everyday human activity.
Organisations spanning geospatial mapping, satellite communications, NASA, the European Space Agency, and commercial ventures that depend on precise timestamps are each facing adjustments ahead of the transition. Governing bodies for global telecommunications standards — the International Telecommunication Union among them — are expected to revise their technical frameworks once UTC drops the leap-second requirement.
Guidance documents and software recommendations are set to come from governments, standards bodies, and industry figures ahead of the changeover, with the aim of keeping the shift on track. Adjustments to operating systems, database management tools, and networking equipment are to be carried out by engineers to accommodate the newly introduced divergence.
