[LEAPSECS] final report of the UK leap seconds dialog

[Tony Finch]

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.

Tony.
-- 
f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/
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