Original URL: http://www.theregister.co.uk/2011/11/03/atomic_time_could_replace_gmt/

UN set to dump GMT for tech-friendly Atomic Time

Just a minute...

By Anna Leach

Posted in Policy, 3rd November 2011 14:44 GMT

Greenwich could lose its place at the centre of global time if a move to "atomic time" is voted in by the International Telecommunication Union in Geneva in January 2012.

Time scientists are discussing the implications of the change today in pre-vote meeting organised by the Royal Society. British newspapers are mulling how British pride would be dented if the riverside patch of South London gets taken out of the centre of world time-keeping. The Sunday Times said that it would truly mark the end of our days as a "Victorian superpower".

Time has been measured by atomic clocks since 1972, but the hyper-accurate clocks do not measure time as experienced by humans on Earth because the planet's rotation is uneven. Currently, the atomic clocks are adjusted to fit into time as humans experience it, with leap seconds every few years pushing the atomic clocks into line with "human time".

The divergence between GMT and Atomic Time is tiny. At the moment, the leap seconds are applied in a stepped scheme.

The current system of leap seconds causes significant difficulties for computer systems that rely on processes being performed in exact sequence. See how Google grappled with the problem here. Mobile phone networks and GPS systems in particular suffer when leap seconds strike. Continuous atomic time would be much easier to manage.

The ITU document says:

The result of the process would be to stop applying leap seconds at an agreed point and permit the difference with UT1 to increase at a rate of approximately one second per year.  The projection by the BIPM for the (UT1 - UTC) difference to accumulate to one hour is approximately 550 years.

In the new system, it is possible there would be leap minutes once or twice a century.

Alternatively we could keep human and atomic clock times running concurrently: "Knowledge of the precise difference between UTC (human time) and UT1 (atomic time) would continue to be monitored so that any user desiring UT1 would have the information to correct his readings of UTC to UT1 should he choose to do so," reads the International Telecommunications Union's proposal. The ITU is the UN's specialised telecommunications agency. 

The implications of the alternatives are being discussed.

One positive outcome for Brits distressed by the loss of our Victorian superpower status is that the end of GMT as an international standard could accelerate the move to keep British Summer Time into the winter, letting us have lighter evenings.

The ITU posed these questions to member states:

So far, the ITU has received replies from just 16 nations for the latest survey (out of a total of 192, 55 of which participate in the formation of UTC). But with 13 in favour of the change, and just three against, the bill looks likely to pass, so far.

Read the document here [.docx download] ®