[LEAPSECS] POSIX and C (Was: Re: ISO Influence)

[Ian Batten]

On 22 Dec 2010, at 23:44, Clive D.W. Feather wrote:


> Ian Batten said:

>> The same applies, mutatis mutandis, to the UK.  MSF broadcasts legal  

>> UK time, summer time corrected when it in force.

> [...]

>> you can recover UTC all year around by subtracting one hour when  

>> appropriate.

> 

> Um, those two statements are contradictory. UK legal time is GMT (i.e. UT),

> *NOT* UTC.


De jure, it is.  De facto, it's UTC, and that was the reason claimed (and as I said a few months ago, I wish I could find the letter I got from Lord Sainsbury) as to why the Labour government didn't proceed with the bill to formalise the switch from GMT to UTC that fell with the Major government.   Practically, there are a lot of scenarios in which an hour matters for legal time, rather fewer a second.


> 

> Checking, I see that MSF transmits UTC but also encodes DUT1, so you can

> derive UK legal time by looking at bits 01B to 16B and *58B.


We used to do that for BT equipment, but they gave up, and now (so far as I know) all the UK telcos tick UTC(GPS).

ian