From alexander.belopolsky at gmail.com  Fri Oct  2 19:45:18 2015
From: alexander.belopolsky at gmail.com (Alexander Belopolsky)
Date: Fri, 2 Oct 2015 13:45:18 -0400
Subject: [Datetime-SIG] Add strptime directives to parse ISO calendar dates
Message-ID: <CAP7h-xanAVAmew3YXFFQvdqvYXqKocKd+ZvG5Ud8cu6sK_ZEdg@mail.gmail.com>

This feature has been proposed four years ago and a complete patch is
available at the bug tracker. [1]

I think this is a nice feature to have and the latest patch looks good, but
it will be helpful to have the patch reviewed by someone who will actually
benefit from this feature.

[1]: http://bugs.python.org/issue12006
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From alexander.belopolsky at gmail.com  Wed Oct 21 23:27:44 2015
From: alexander.belopolsky at gmail.com (Alexander Belopolsky)
Date: Wed, 21 Oct 2015 17:27:44 -0400
Subject: [Datetime-SIG] Visualizing the DST transitions
Message-ID: <CAP7h-xbDLyKteoqJ0S0Tu3BmE66tO8HdAsV0cBPYWW5eFU4uiw@mail.gmail.com>

I just wanted to share a slide
<https://docs.google.com/presentation/d/1H1tkvg_vm39jXPZbOvQLoWb32POSpTYiZx8qMtBvdSQ/pub?start=false&loop=false&delayms=3000&slide=id.gdfc9fbb2b_0_74>
[1] I came across that is very similar to the sketches in PEP 495.  Does
anyone understand how CCTZ handles the discontinuities?

[1]:
https://docs.google.com/presentation/d/1H1tkvg_vm39jXPZbOvQLoWb32POSpTYiZx8qMtBvdSQ/pub?start=false&loop=false&delayms=3000&slide=id.gdfc9fbb2b_0_74
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From guido at python.org  Wed Oct 21 23:29:58 2015
From: guido at python.org (Guido van Rossum)
Date: Wed, 21 Oct 2015 14:29:58 -0700
Subject: [Datetime-SIG] Visualizing the DST transitions
In-Reply-To: <CAP7h-xbDLyKteoqJ0S0Tu3BmE66tO8HdAsV0cBPYWW5eFU4uiw@mail.gmail.com>
References: <CAP7h-xbDLyKteoqJ0S0Tu3BmE66tO8HdAsV0cBPYWW5eFU4uiw@mail.gmail.com>
Message-ID: <CAP7+vJJCNKxxqg9-ucq1QjFtTXT=x3w=n0Hx_SFACvL0P8B3Zg@mail.gmail.com>

Heh, they swapped the X and Y axes. :-)

On Wed, Oct 21, 2015 at 2:27 PM, Alexander Belopolsky <
alexander.belopolsky at gmail.com> wrote:

> I just wanted to share a slide
> <https://docs.google.com/presentation/d/1H1tkvg_vm39jXPZbOvQLoWb32POSpTYiZx8qMtBvdSQ/pub?start=false&loop=false&delayms=3000&slide=id.gdfc9fbb2b_0_74>
> [1] I came across that is very similar to the sketches in PEP 495.  Does
> anyone understand how CCTZ handles the discontinuities?
>
> [1]:
> https://docs.google.com/presentation/d/1H1tkvg_vm39jXPZbOvQLoWb32POSpTYiZx8qMtBvdSQ/pub?start=false&loop=false&delayms=3000&slide=id.gdfc9fbb2b_0_74
>
> _______________________________________________
> Datetime-SIG mailing list
> Datetime-SIG at python.org
> https://mail.python.org/mailman/listinfo/datetime-sig
> The PSF Code of Conduct applies to this mailing list:
> https://www.python.org/psf/codeofconduct/
>



-- 
--Guido van Rossum (python.org/~guido)
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From alexander.belopolsky at gmail.com  Wed Oct 21 23:42:15 2015
From: alexander.belopolsky at gmail.com (Alexander Belopolsky)
Date: Wed, 21 Oct 2015 17:42:15 -0400
Subject: [Datetime-SIG] Visualizing the DST transitions
In-Reply-To: <CAP7+vJJCNKxxqg9-ucq1QjFtTXT=x3w=n0Hx_SFACvL0P8B3Zg@mail.gmail.com>
References: <CAP7h-xbDLyKteoqJ0S0Tu3BmE66tO8HdAsV0cBPYWW5eFU4uiw@mail.gmail.com>
 <CAP7+vJJCNKxxqg9-ucq1QjFtTXT=x3w=n0Hx_SFACvL0P8B3Zg@mail.gmail.com>
Message-ID: <CAP7h-xYU8-qKA+AEAZQEt5bRc6pS7VdwcuTxzoWgkNE+L49U5w@mail.gmail.com>

On Wed, Oct 21, 2015 at 5:29 PM, Guido van Rossum <guido at python.org> wrote:

> Heh, they swapped the X and Y axes. :-)


Right, but despite that, it looks like they use the same default rules for
local to absolute conversions as we do in PEP 495 datetime.timestamp().
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From carl at oddbird.net  Wed Oct 21 23:42:26 2015
From: carl at oddbird.net (Carl Meyer)
Date: Wed, 21 Oct 2015 15:42:26 -0600
Subject: [Datetime-SIG] Visualizing the DST transitions
In-Reply-To: <CAP7h-xbDLyKteoqJ0S0Tu3BmE66tO8HdAsV0cBPYWW5eFU4uiw@mail.gmail.com>
References: <CAP7h-xbDLyKteoqJ0S0Tu3BmE66tO8HdAsV0cBPYWW5eFU4uiw@mail.gmail.com>
Message-ID: <562806C2.8030204@oddbird.net>

On 10/21/2015 03:27 PM, Alexander Belopolsky wrote:
> I just wanted to share a slide
> <https://docs.google.com/presentation/d/1H1tkvg_vm39jXPZbOvQLoWb32POSpTYiZx8qMtBvdSQ/pub?start=false&loop=false&delayms=3000&slide=id.gdfc9fbb2b_0_74> 
> [1] I came across that is very similar to the sketches in PEP 495.  Does
> anyone understand how CCTZ handles the discontinuities?

It provides two APIs, MakeTime and MakeTimeInfo, which both accept a
"naive datetime" and a timezone.

MakeTime returns an absolute time, and discontinuities are handled by
always assuming the pre-transition offset:
https://github.com/google/cctz/blob/master/src/cctz.h#L131

MakeTimeInfo returns a more complex TimeInfo struct which has a `kind`
enum member that can be `UNIQUE` (the normal case), `SKIPPED`, or
`REPEATED`, and has `pre`, `post`, and `trans` timestamp members
(containing the time calculated using the pre-transition offset, the
time calculated using the post-transition offset, and the time at which
the transition occurs), which in the normal case of `UNIQUE` are all set
to the same value. Documentation starts here:
https://github.com/google/cctz/blob/master/src/cctz.h#L142

Carl

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