[LEAPSECS] presentations from AAS Future of Time sessions

[Joseph Gwinn]

On Sun, 12 Jan 2014 10:58:40 +0000, Poul-Henning Kamp wrote:

> In message <52D257B6.6090900 at edlmax.com>, Brooks Harris writes:

> 

>>> But time_t has always been UTC, because it was meant to be UTC.

>> 

>> Oh, I see what you're saying. Of course - UTC in the historical non-Leap 

>> Second period existed, and they intended time_t to reflect it.

> 

> Nice try to twist things to your own viewpoint, but you are wrong.

> 

> They meant UTC to be UTC.

> 

> They had absolutely no opinion on leapseconds.


The original UNIX definition of the Epoch invoked GMT, and POSIX 
updated this to UTC as it was the obvious successor.  The POSIX crowd 
chose to ignore leap seconds, because one cannot expect an isolated 
system to know of such things, and it was not necessary to know to meet 
the requirements of UNIX/POSIX time, chiefly file modification 
timestamps to ensure (to within one second) causal time ordering. 
One-second resolution was fine enough to ensure causal order when the 
policy was adopted, but this fell apart in the 1980s.



> Leapseconds, UT, UT1, UT2 or for that matter astronomers or their

> opinions about time, played absolutely no role in the decision

> making process.


GMT is now (unofficially?) deemed to be UT1.

In practice, for probably the majority of systems, the time source is 
the user's wristwatch.

 

> Bell Labs were a telco-sidekick and the telco business used UTC

> to isolate local timezones and DST issues to a presentation issue.

> 

> Do I need to remind you that it was telcos caused UTC to be CCITT

> business in the first place ?

> 

> Apparantly the only computing person outside timelabs who cared

> about leapseconds prior to 1985 was Dave Mills.


Could be.


Joe Gwinn