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Re: timestamp resolution

From: Giacomo A. Catenazzi
Subject: Re: timestamp resolution
Date: Thu, 10 May 2007 15:29:51 +0200
User-agent: Thunderbird (Windows/20070221)

Hans Aberg wrote:
On 9 May 2007, at 16:30, Joseph M Gwinn wrote:

In fact, POSIX "Seconds Since the Epoch" is effectively TAI minus an
unspecified offset because POSIX counts ~SI seconds regardless of
astronomy and thus leap anything.

I think the specs ignore the issue, so it is only accurate within a couple of ten seconds. I figure typical system just ignore the leap seconds from the epoch, and adjusts the internal clock on the first lookup after the time server has changed. It is these jumps in the internal clock that may pose a problem: it is hard to tell which computer that have adjusted and which have not.

What do you mean with "internal clock"? If you means "the hardware
clock", ignore it.  Systems usually save and restore times in hw
clocks only on reboots, so they use the same convention to save
and restore times, so it is not a problem (but eventually with a
networked file system, with the machine down between leap second and
update of the leap-second file).

It really depend on interface of the hardware clock: if clocks support
seconds (since epoch) or if you should use a MM/DD/(YY)YY HH:mm:ss
interface, and I doubt POSIX could change such hardware capabilities/


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