Press release

Leap seconds away from having your say on time management

Leap seconds: Launch of a public dialogue on the future policy.

Image of clock and earth
Image: ‘Clockwork earth’ courtesy of Ben Gilliland , editor CosmOnline.

Science and Universities Minister David Willetts on 14 May 2014, has launched a public dialogue on leap seconds, to help inform future policy on this timely issue.

Currently, leap seconds are added to or removed from the international coordinated timescale (UTC), keeping it in sync with solar time, based on the position of the sun.

Because the periodic insertion of leap seconds can cause problems to systems such as computers and communications networks, there have been proposals to cease its use. This could result in a gradual separation of solar time and UTC.

Science Minister David Willetts said:

My view is that without leap seconds we will eventually lose the link between time and people’s everyday experience of day and night and this public dialogue will give everyone the opportunity to have their say on this important issue. It will also help to inform our position ahead of next year’s decision on the future of leap seconds.

In 2015 the International Telcommunications Union (ITU) will take a decision about whether UTC should continue to be aligned with solar time or move to rely fully on atomic clocks.

This decision will be taken after the culmination of many years of discussion amongst those using highly accurate time for technical purposes, but no international agreement has been reached to date.

The general public are invited to be part of an open discussion on a dedicated leap seconds dialogue website from today.

The National Measurement Office (NMO), an Executive Agency of the Department for Business, Innovation and Skills (BIS), working with Sciencewise, has commissioned OPM Group to run this dialogue.


  1. the national public dialogue will also involve workshops throughout the UK; arrangements for recruiting attendees for these have already been made in order to ensure a good cross section of the public is included, therefore applications are not being sought

  2. since 1972, leap seconds have been used to align UTC with solar time


The Department for Business, Innovation and Skills (BIS) is the department for economic growth. The department invests in skills and education to promote trade, boost innovation and help people to start and grow a business. BIS also protects consumers and reduces the impact of regulation. For more information on BIS.


NMO is responsible for managing and developing the National Measurement System (NMS) which is a network of laboratories and processes that provide measurement standards and calibration testing facilities. It maintains the measurement infrastructure, represents the position of the UK internationally and influences the development of standards. For more information on the responsibilities of NMO.


The current atomic clock system at the National Physical laboratory (NPL) is the basis of UK time, and the cutting-edge research being carried out is working to improve timekeeping accuracy even further. For more information.


Sciencewise is a fully funded programme of BIS and was set up in response to the debates over Genetic Modification in food in 2004 to create public dialogues. Here is some information about past Sciencewise projects.

Public dialogues

The government commissions ‘public dialogues’ around science questions which have a delicate ethical balance or where there is an out and out dilemma. When given the right materials and, vitally, access to a cross section of specialists and positions, the public tend to take these exercises very seriously and often come up with very helpful suggestions on ways forward. For a participant, Sciencewise dialogues are a bit like jury service but collaboratively working with scientists and policy makers rather than adversarially working to bring the other side down.

OPM For more information on the OMP Group.

BIPM For more information on BIPM.

ITU For more information on ITU

Background to leap seconds

The timescale readily available in the UK is Coordinated Universal Time (UTC). This timescale is used internationally, with an offset of the appropriate number of hours for each time zone or to implement daylight saving time. UTC is maintained by a number of atomic clocks around the world, and is computed by the Bureau International des Poids et Mesures (BIPM). UTC makes use of the atomic definition of the SI second, which was introduced in 1967 and is effectively equivalent to the astronomical second based on a mean solar day of 86,400 seconds in about 1820.

Historically, time has been determined by the rotation of the earth and the location of the sun in the sky; in Greenwich Mean Time (GMT) noon is defined to be the mean time the sun reaches its highest point in the sky in Greenwich. However, the rotation of the earth is irregular and is also slowing—the length of the day is now (averaged out over several years) around 2.5 milliseconds longer than it was in 1820. This means that any time standard determined by accurate measuring devices like atomic clocks (such as UTC) slowly falls out of sync with solar time. In order to keep the two in sync leap seconds are added to (or, in principle, removed from) UTC to adjust for the irregularity in the earth’s rotation. This ensures that UTC does not come apart from GMT by more than 0.9 seconds. There have been 25 leap seconds since they were first introduced in 1972.


Niall Boyle or Paul Broadbent

Published 14 May 2014