[LEAPSECS] Back to Basics

[Ian Batten]

On 3 Nov 2010, at 17:59, Steve Allen wrote:


> On Wed 2010-11-03T13:46:02 -0400, ashtongj hath writ:

>> But I could write a contract specifying UTC and I strongly suspect

>> it would be enforced.

> 

> In that case all POSIX systems are illegal and would be

> subject to confiscation or shutdown.


A contract is only enforced when a party wants it to.

These days, [major UK telco] uses GPS and adopts a "legal time?  Show me a source of UT1 and I might believe it's UK legal time, otherwise UTC(GPS) is fine" attitude.  But back in the day, it used to use Trutime receivers slaved to MSF, which broadcasts UTC(NPL) with DUT1 available in the signal.  So a management or billing platform connected to such a receiver has the choice of ticking UTC(NPL) or something closely approximating UT1.  If it decides to tick UTC(NPL), it also has the choice of either treating leap-seconds specially (by some means) as they are announced, or of taking the attitude that they are corrected as an unexpected slew in time over the hour following.  

As I was responsible for interfacing the boxes to our products, I asked [major UK telco] which (given the contract said "UK legal time +/- 1s") permutation of those options they wanted.  Their response?  They didn't care.  The requirement was to show due diligence for billing for things like "when does cheap rate start" and "when does Sunday start".  Provided it was close enough, they weren't going to go looking for things to sue their suppliers over.

They were, in any case, far more concerned about summer-time, where the potential for 3600 seconds of billing at the wrong rate was much more serious.

ian