[LEAPSECS] LEAPSECS Digest, Vol 45, Issue 3

Ian Batten igb at batten.eu.org
Fri Sep 3 02:35:34 EDT 2010

On 3 Sep 2010, at 02:28, Tony Finch wrote:

> On 2 Sep 2010, at 22:03, Ian Batten <igb at batten.eu.org> wrote:


>> De facto UK time is UTC; de jure is UT, probably UT1.


> De jure it is "Greenwich mean time". AIUI when GMT was last

> maintained as a solar timescale it did not correspond exactly to

> modern UT1 nor UT2, though it was similar.


> How does UTC+DUT1 relate to UT1?

I have searched my records, but it appears that --- and this may prove
to be Something Of An Oversight --- I didn't keep the correspondence I
had with the science minister in about 2000 about the UTC/GMT
legislation that had been dropped in 1997. My clear memory is that
Lord Sainsbury's response to my proposal that the government should
resurrect and give time to passing the legislation was summarised a
few hours ago by Daniel Tobias:

> They can get away with that now, as the difference between the two is

> too small to matter except to some highly specialized professions

> whose issues haven't happened to come before the courts.

I think the form of words from the minister was that the difference
between GMT and UTC was small enough that the only people to whom it
mattered had domain-specific means to resolve the uncertainty, so the
practical effect on the country at large was not worth the legislative
effort. Which is effectively a |DUT1|<1 argument, although as people
are pointing out the relationship between DUT1 and GMT isn't as clear
as I thought.

I confess I hadn't, until you and others pointed it out, thought
through the issue of GMT not being clearly UT1, nor the difference in
resolution between on-time marker resolution and DUT1 resolution, so I
think I'm now less sure of the de jure position than I was.


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