[Ietf-calsify] definitive references for UTC

[Mike Samuel]

Most existing date libraries ignore leap seconds, so it's unlikely
that systems built on these will handle them.

I don't think that 2445 uses a <units-since-epoch> representation of
dates, so the only place where UTC enters the picture is in durations
-- subtracting dates, and adding durations to dates.  One alternative
to specifying a different interpretation of UTC, would be to mandate
that PT60S == PT1M.

Here's a quick survey of leap second support in common platforms/libraries:

http://www.mail-archive.com/leapsecs@rom.usno.navy.mil/msg00109.html
    Distributing leap second tables and requiring hosts to be "on-line"
    to receive them in those days (when UUCP over slow baud modems was
    common) was not considered realistic.  It was felt expect vendors
    and/or system administrators to maintain a complete leap second table
    (including leap seconds announced in advance) was also considered
    unrealistic.

    The POSIX decision was to preserve existing practice.  That the
    vast majority of time-stamp calculation methods ignored leap seconds .
    The decision was to to continue to use a trivial seconds since the
    Epoch" calculation that ignored leap seconds.

http://joda-time.sourceforge.net/faq.html#leapseconds
    Joda-Time does not support leap seconds. Leap seconds can be supported by
    writing a new, specialized chronology, ...

http://docs.python.org/lib/datetime-date.html
    Note that on non-POSIX systems that include leap seconds in their
notion of a
    timestamp, leap seconds are ignored by fromtimestamp().

Similarly java.util.Date only supports leap seconds if the underlying
hardware does.


cheers,
mike


On 26/03/07, Bill Kearney <wkearney99 at hotmail.com> wrote:
>
> > Although it's tempting to make one
> > protocol shoe fit multiple application feet, the result is rarely
> > satsifactory and usually is a wretched compromise that serves nobody.
>
> +1
> _______________________________________________
> Ietf-calsify mailing list
> Ietf-calsify at osafoundation.org
> http://lists.osafoundation.org/mailman/listinfo/ietf-calsify
>