[tz] leap second theory
Brian Inglis
Brian.Inglis at SystematicSw.ab.ca
Sun Aug 18 00:23:00 UTC 2019
On 2019-08-17 17:38, Howard Hinnant wrote:
> On Aug 17, 2019, at 4:45 PM, Paul Eggert <eggert at cs.ucla.edu> wrote:
>> … the 'leapseconds' file, which nowadays is used more often than the
>> direct approach, or at least that's my impression.
>
> Here’s another data point for you:
> http://eel.is/c++draft/time.clock.utc.overview#1
> This is the draft C++20 spec which specifies two clocks:
> 1. system_clock: Models Unix Time (does not count leap seconds).
> 2. utc_clock: Counts leap seconds.
> And provides bidirectional mappings between these two sets of time points.
> And the easiest way to implement that mapping is to read in the IANA tz
> leapseconds file.
WG14/C is looking at:
http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2402.pdf
which seems somewhat based on the POSIX standard.
The POSIX Austin CSRG is discussing clarifying tm_isdst:
https://www.mail-archive.com/search?q=time&l=austin-group-l%40opengroup.org
and other issues.
--
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
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