UTC as basis for time legislation

Tobias Conradi tobias.conradi at gmail.com
Mon Sep 26 14:27:58 UTC 2011

On Mon, Sep 26, 2011 at 4:13 PM, Clive D.W. Feather <clive at davros.org> wrote:
> Tobias Conradi said:
>>> No, the law here says legal time is GMT, but most official time signals
>>> are UTC. There have been a few unsuccessful attempts to deal with the
>>> mismatch between de jure and de facto UK time, e.g.
>>> http://www.publications.parliament.uk/pa/ld199798/ldhansrd/vo970611/text/70611-10.htm
>> So there is one flavor of GMT that is UTC and there is legal GMT which
>> is something different.
> Yes and no.
Which part you refer to by "no"?

>> 2011i/tzdata equates GMT for 2011 with UTC.
> In effect, yes. It takes the view that the difference is too small to
> matter *in this context*.
I personally would rather not guess what view it has, but stick to what it does.

>>>> So if country A says its legal time is an hour ahead of GMT and B says
>>>> they are an hour ahead of UTC, those are technically different statements.
>> To my understanding the statement of country A is ambiguous. Whether
>> there is approximation in tzdata depends on how one interprets the the
>> statement of country A.
> No. The statement of country A is *not* ambigous (except at the millisecond
> level as mentioned above).
Since there are different types of GMT it is. There is the legal GMT
which is ambiguous in itself and the BBC-GMT.

> The statements are technically and de jure
> different.
Yes, the first is ambiguous.

>Whether country A actually meant UTC when it wrote GMT is a
> separate question that you'd have to ask country A.
>> This has nothing to do with ITU-R TF.460-6.
> But the proposed amendment to it would mean that "too small to matter in
> this context" will cease to be true eventually.
GMT is not mentioned in the document

Also, since there is a time span when GMT was legally defined
different from UTC, I think an ITU document cannot change that

In the linked document I also see no change of definition of UTC.

Tobias Conradi
Rheinsberger Str. 18
10115 Berlin


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