[LEAPSECS] Civil timekeeping before 1 January 1972

[Brooks Harris]

On 2015-03-07 06:50 PM, Joseph Gwinn wrote:
> On Sat, 07 Mar 2015 14:14:07 -0500, Brooks Harris wrote:
>> In the discussions I've been involved with many people argued
>> strenuously "we don't care about the past, only accurate date-time
>> going forward!". The reason I'm choosing to ignore the subject of
>> accurate date-times before 1972 is not that its not important, but
>> probably the same reason its side-stepped by NTP, PTP, POSIX, and GPS
>> - its just too expansive a topic to tackle in some commonly accepted
>> way. For date-time before 1972 you've got to switch to some other
>> timescale depending on the purpose at hand.
> I figured it out the difference between GMD and UTC for POSIX.  There
> was an 81 microsecond error,  At the time, most UNIX boxes kept time to
> the nearest second, synchronized to a hairy wrist.  There were advanced
> systems that could do milliseconds, and in the 1980s a few that had
> microsecond resolution, but we chained them to GPS via NTP, so the
> error was multiple milliseconds, depending on everything.
Hi Joe,

I see the difficulties with UTC implementations and the questions at 
ITU-R stemming from the historical and legacy misalignment of the 
timekeeping mechanisms of the c language and POSIX and the UTC 
specifications. Perhaps that's obvious. I'm not criticizing anybody 
anywhere for this, its just the way its come about.

I think the only way the industry can eventually converge on reliable 
"civil time" representation is to refine the underlying time mechanisms 
in POSIX in some manner that allows a migration to a more comprehensive 
UTC implementation. I think if a new new POSIX time specification were 
to take shape it would add an option to the the conversation at ITU-R - 
instead of simply "to kill Leap Seconds or not" they'd also have "a 
viable migration path to comprehensive UTC timekeeping implementation" 
to consider.

We understand the folks at POSIX have grappled with this topic in the 
past and run into all sorts of difficulty. Given the current state of 
affairs, do you think there's any way IEEE and POSIX could reengage this 
topic?

-Brooks

>
> Joe Gwinn
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