On 2014-01-19 08:26 AM, Warner Losh wrote:
On Jan 18, 2014, at 11:03 PM, Brooks Harris wrote:
On 2014-01-18 08:53 AM, Warner Losh wrote:
On Jan 18, 2014, at 6:31 AM, Magnus Danielson wrote:
On 18/01/14 11:56, Poul-Henning Kamp wrote:
In message <52da2a0f.9060...@rubidium.dyndns.org>, Magnus Danielson writes:
If you where right about not basing it on the orbital debris, then we
should not attempt to be using concepts like seconds, minutes, hours,
days, weeks, months, years [...]
As you are no doubt aware, the POSIX time_t does not do that.
The POSIX time_t still tries to encode it, using some of the rules that makes of UTC,
including SI-seconds. However, the argument was not about POSIX time_t, but about what
"Universal" in UTC actually means.
POSIX time_t is explicitly not UTC.
Ah, well, it is explicitly UTC, but not the UTC we'd like.
section 3.150 Epoch says - "The time zero hours, zero minutes, zero seconds, on
January 1, 1970 Coordinated Universal Time (UTC).
No. It is *NOT* UTC. It omits leap seconds. It confuses the issue by using the
term UTC when it specifies something that doesn't actually model UTC, but only
an approximation of it, not the actual UTC. It makes matters worse by
specifying a UTC epoch.
But its described behavior is not *modern* UTC (with Leap Seconds), and this is
made clearer by section A.4.15 Seconds Since the Epoch -
That's rather my point. It is most definitely not UTC.
"Coordinated Universal Time (UTC) includes leap seconds. However, in POSIX time
(seconds
since the Epoch), leap seconds are ignored (not applied) to provide an easy and
compatible
method of computing time differences. Broken-down POSIX time is therefore not
necessarily
UTC, despite its appearance."
POSIX time_t isn't UTC. Broken down time isn't UTC either.
"Broken-down POSIX time" is a YY-MM-DD hh:mm:ss representation - a *calendar*
date-time.
POSIX behaves as an *uncompensated-for-Leap-Seconds* Gregorian calendar
counting scheme.
Right, this is *NOT* UTC. That's why I said that it is explicitly not UTC. It
says so in the standard.
We agree. The standard first explicitly says that it is UTC and then it
explicitly says it is *not* UTC. Why should there be any confusion
about this? :-)
-Brooks
I just left out the word 'necessarily' because it could become UTC if UTC started
omitting leap seconds and retained the name UTC for "slide of hand" reasons.
But politics and sentiment are against such a change in that way.
Warner
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