[LEAPSECS] Caveat emptor!

[Joseph S. Myers]

On Tue, 12 Apr 2011, Ian Batten wrote:


> I think it's messier than that.  De facto UK time is UTC, as we've 

> discussed, but the only source of de jure legal time now is MSF: it 

> broadcasts UTC(NPL), but DUT1 is available in the payload (and that's 


It broadcasts de facto UK clock time, UTC(NPL) in winter and UTC+1(NPL) in 
summer, with a summer time bit but without any other indication of the UTC 
offset.  Any clock that thinks it is recovering UTC(NPL) from this signal 
is probably assuming that winter time will always be UTC+0 and summer time 
will always be UTC+1.  What happens to the signal if the UK moves to 
UTC+1/UTC+2 is documented

http://www.npl.co.uk/science-+-technology/time-and-frequency/time/msf-time-date-code

"In the event of UK civil time undergoing an additional permanent offset, 
bit *58B will need to be changed once without any corresponding change in 
UK clock time."

but a receiver would need to remember this information from the time of 
the change, as the subsequent time signals would have no indication that 
it had happened.

-- 
Joseph S. Myers
jsm at polyomino.org.uk