Re: Predictable Internet Time

Joe Touch <touch@isi.edu> Wed, 04 January 2017 00:07 UTC

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Subject: Re: Predictable Internet Time
To: Tony Finch <dot@dotat.at>
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From: Joe Touch <touch@isi.edu>
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Date: Tue, 3 Jan 2017 16:07:25 -0800
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On 1/3/2017 4:00 PM, Tony Finch wrote:
>
> Joe Touch <touch@isi.edu>; wrote:
> >
> > The Posic spec describes how to convert seconds since epoch to UTC; it
> > is that conversion where leap seconds come into play.
>
> No, it describes the reverse, how to convert broken-down UTC time to
> seconds since the epoch.

You're right; I got it backwards. Except it admits it's an approximation:
"A value that approximates the number of seconds that have elapsed since
the Epoch."

> > > But if the count of seconds includes the leap second, surely the
> > > number representing the leap second could be printed properly as :60 ?
> >
> > UTC defines it that way, so if you want to output the correct UTC value,
> > that is the only solution.
>
> UTC does not define a seconds count

UTC includes :60 as a valid time, as was indicated in the leap-second
announcement.

However, when you are computing epoch time from UTC, you'd have to
account for the leap seconds since epoch to correct for the difference
in actual elapsed seconds.

Joe