[LEAPSECS] final report of the UK leap seconds dialog

[Ian Batten]

> On 9 Feb 2015, at 12:43, Tony Finch <dot at dotat.at> wrote:
> 
> Ian Batten via LEAPSECS <leapsecs at leapsecond.com> wrote:
>> 
>> An obvious example is the UK.  Our legal time is GMT with DST, usually taken to be
>> UT1 with DST.  Our "de facto" civil time is UTC with DST, and over the years this
>> has become more and more ingrained (the "Greenwich" pips on the hour on Radio 4
>> are now UTC, the MSF transmitter is UTC with a 0.1s resolution DUT1 embedded in
>> the data stream, etc, etc).  Everyone calls it GMT, and government discussions
>> about leapseconds are often in terms of GMT (yes, obviously a nonsense), and the
>> law definitely calls it GMT, but here we are: custom and practice makes it UTC.
> 
> My understanding from reading a history of the Greenwich Observatory at
> Herstmonceux is that the UK Government's official time signals (from the
> RGO and NPL) were UTC since the 1960s, and switched to leap seconds in
> 1972. Before UTC, GMT was UT2. (I don't know when GMT was last equivalent
> to UT1.)
> 
> GMT's specification has changed several times, so it is not "obviously" a
> nonsense to make it equivalent to UTC. It is still a mean time, though
> it prioritizes frequency stability at the cost of larger phase differences.

Sorry, what I mean by "obviously a nonsense" is that a Mean Time won't have
leap seconds, so discussing "should we keep adding leap seconds to GMT" is
nonsense.  The question is as we all know "should we keep adding leap seconds 
to UTC to keep it close to mean time".

ian