Re: REMINDER: LEAP SECOND

["Gary E. Miller" <gem () rellim com>]

Yo Jay!

On Tue, 23 Jun 2015 22:02:50 -0400 (EDT)
Jay Ashworth <jra () baylink com> wrote:

> ----- Original Message -----
> > From: "Harlan Stenn" <stenn () ntp org>
>
> > > You misunderstand the problem. :) The problem is not "clock skips
> > > backward one second," because most of the time that's not what
> > > happens. The problem is that most software does not handle it well
> > > when the clock ticks ... :59 :60 :00 instead of ticking directly
> > > from
> > > :59 to :00.
> >
> > POSIX NEVER shows :60.
>
> Then I hope POSIX does not claim to represent UTC, because UTC does,
> no?

POSIX-1:2001 clearly 61 seeconds in a minute:

The POSIX-1:2001 docs are here:
    http://pubs.opengroup.org/onlinepubs/009695399/basedefs/time.h.html

From the Description:

    "The <time.h> header shall declare the structure tm, which shall
    include at least the following members:

    int    tm_sec   Seconds [0,60]. "

From the Application Usage:

    "The range [0,60] for tm_sec allows for the occasional leap second."

From the Rationale:

    "The range [0,60] seconds allows for positive or negative leap seconds."

But, from the section on "Seconds Since the Epoch"

http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap04.html#tag_04_14

POSIX seconds is defined as:

    tm_sec + tm_min*60 + tm_hour*3600 + tm_yday*86400 +
        (tm_year-70)*31536000 + ((tm_year-69)/4)*86400 -
        ((tm_year-1)/100)*86400 + ((tm_year+299)/400)*86400

Summed up with:

    "The relationship between the actual time of day and the current
    value for seconds since the Epoch is unspecified."

Which basically says if you are gonna split hairs on leap seconds
things will be undefined.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        gem () rellim com  Tel:+1(541)382-8588

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