The world’s official time standard is set to change after international timekeepers approved the end of leap seconds from 20 May 2027. The decision is designed to reduce risks for computer networks, telecommunications, satellite navigation and other systems that depend on uninterrupted time synchronisation.
The resolution was adopted on 15 October 2026 at the 28th meeting of the General Conference on Weights and Measures (CGPM) in Versailles. From the implementation date, Coordinated Universal Time (UTC) will continue without occasional one-second adjustments, while the difference between atomic clock time and the Earth’s rotation will gradually increase.
Why are leap seconds being removed?
Leap seconds were introduced to keep two different measures of time broadly aligned. UTC is calculated using highly precise atomic clocks, while astronomical time is based on the Earth’s rotation. Because the planet does not rotate at a perfectly constant speed, the two systems can slowly drift apart.
Since 1972, 27 leap seconds have been added to UTC. The most recent occurred at the end of 2016. During a leap-second adjustment, a minute can contain 61 seconds rather than the usual 60.
Although the change is imperceptible in daily life, it creates complications for digital infrastructure. Computer operating systems, financial networks, telecommunications, satellite services and electricity systems must coordinate events with extreme precision. An irregular extra second can be difficult for software and hardware to process consistently.
What prompted the new timekeeping rules?
The CGPM decision also reflects concern about the possibility of a negative leap second. In that scenario, one second would be removed from UTC rather than added.
Over long periods, tidal forces generally slow the Earth’s rotation. However, the planet has also experienced periods in which it rotated slightly faster. That raised the prospect that a negative leap second could eventually be required for the first time.
Because no negative leap second has ever been implemented, experts could not be certain that global technical systems would handle it reliably. Ending leap-second adjustments avoids that immediate risk and provides a more predictable framework for digital systems.
UTC will continue, but its link to Earth’s rotation will loosen
Under the new arrangement, UTC will remain the international reference for civil time, but it will no longer be regularly corrected to stay closely aligned with astronomical time. The difference could eventually grow to as much as 3,600 seconds, or one hour.
That increase is not expected to happen soon. The decision is therefore primarily precautionary: it removes an irregular technical adjustment now while allowing experts to consider how any much larger divergence should be managed in the future.
Which sectors will be affected?
Most people will not notice a direct change to clocks, phones or watches. The main impact will be felt by specialist industries and scientific fields that require exceptionally precise time references.
- Computer and communications networks: systems will no longer need to process unpredictable extra seconds.
- Satellite navigation: timing calculations can use a continuous UTC scale.
- Power infrastructure: grid operators can avoid complications caused by irregular time adjustments.
- Astronomy and geodesy: researchers will continue tracking the Earth’s rotation separately from civil time.
- Space and satellite applications: operators will need to account for the growing difference between UTC and astronomical time where relevant.
What does the decision mean for the UK and Europe?
The change is an international technical decision, not a new European law or a change to national time zones. The United Kingdom, like other countries using UTC as a reference, will continue to use its existing arrangements.
Seasonal clock changes are unaffected. In the UK, winter time will continue to follow Greenwich Mean Time, while British Summer Time will remain one hour ahead during the summer period. The abolition of leap seconds should not be confused with debates about daylight-saving time or the annual switch between summer and winter clocks.
European countries represented in the CGPM include Germany, Austria, France, Italy, Spain, Switzerland, the UK, Poland and Ukraine, among others. However, the resolution applies through the international timekeeping system rather than through a separate European Union measure.
What is the General Conference on Weights and Measures?
The General Conference on Weights and Measures is the governing conference linked to the international measurement system. It brings together representatives of member states and associated states and economic areas, generally meeting every four years.
The International Bureau of Weights and Measures says the organisation currently includes 69 member states and 34 associated states and economies. Its work covers internationally agreed measurement standards, including the systems used to define and disseminate precise time.
Why does the decision matter?
The move prioritises stability for the digital infrastructure that supports modern economies. A continuous time scale is easier for software developers, network operators and satellite service providers to manage than one that occasionally includes an unexpected extra or missing second.
Scientists will still need accurate information about the Earth’s rotation. The difference is that astronomical observations will increasingly be treated as a separate reference rather than being maintained through leap-second corrections to UTC.
The change is unlikely to affect everyday schedules, travel timetables or the time shown on ordinary devices from 2027. Its importance lies in the underlying systems that coordinate communications, computing, navigation and infrastructure across borders.
What happens next?
The new approach is scheduled to begin on 20 May 2027. Technical organisations and scientific communities will then continue developing methods for monitoring and managing the growing gap between UTC and astronomical time.
The key takeaway from this Europe news development is that leap seconds will disappear from the international civil-time system, but ordinary clocks and seasonal time changes will continue as before. The reform is intended to make global digital timekeeping more reliable while leaving specialist users responsible for tracking the Earth’s changing rotation.
