The Future of Leap Seconds

Leap seconds are added to our clocks to compensate for the Earth's slowing rotation.
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However, some scientists propose abolishing leap seconds in the future, redefining the way we measure time. This issue will be put to a vote in 2015.

A leap second will be added in June 2012

Should the planet's rotation define time on Earth?

Triggered by a questionaire about Coordinted Universal Time (UTC) distributed by the IERS in 1999, scientists around the world began discussing the use of leap seconds. The argument revolves around the question:

Should we adjust our clocks to the Earth's slowing rotation, or should
atomic clocks be solely responsible for measuring time?

A never-ending argument?

The scientific community has so far failed to reach an agreement on this topic.

• In 2003, a meeting named “ITU-R SRG 7A Colloquium on the UTC timescale” took place in Torino, Italy, where it was suggested that time be decoupled from the Earth’s rotation and leap seconds be abolished. No decision was reached.
• In 2005, US scientists proposed to eliminate leap seconds and replace them with leap hours. The proposal was criticized for its lack of consistent public information and adequate justification.
• In 2012, delegates of the World Radiocommunication Assembly in Geneva, Switzerland, decided once more to postpone the decision to abolish leap seconds and scheduled a new vote for 2015.

Leap seconds: pros and cons

Dr Markus Kuhn (University of Cambridge) lists the following arguments against leap seconds:

• Leap seconds could cause disruptions where computers are tightly synchronized with UTC.
• Leap seconds are a rare anomaly, which is a concern for safety-critical real-time systems (e.g. air-traffic control concepts entirely based on satellite navigation).
• Astronomical time (UT1) is not significant in most people’s daily lives.

His arguments in favor of leap seconds include:

• There have been no credible reports about serious problems caused by leap seconds.
• Some computerized systems that work with leap seconds are costly to modify (eg. antennas that track satellites).
• Computer errors caused by leap seconds can be avoided simply by using International Atomic Time (TAI) instead of Universal Coordinated Time (UTC).
• Desktop computers and network servers have no trouble coping with leap seconds.
• Humankind has defined time by the Earth's rotation for over 5000 years – this tradition should not be given up because of unfounded worries of some air-traffic control engineers.
• Abandoning leap seconds would make sundials obsolete.

Despite calls by some people to retain leap seconds, atomic time advocates also argued that leap seconds were a burden because they were unpredictable.