[Datetime-SIG] What's are the issues?

[Tim Peters]

[TIm]
>> Nope, that's mistaken on both counts, but it is technical.  What I
>> said is correct in all respects given the current code.

[:Lennart]
> That the current code works as designed is not really the issue we
> discuss here, though.
>
> And then you start discussing conversions, which wasn't the issue, it
> was arithmetic.

Lennart, you replied to a quote from me which was specifically and
only talking about timezone conversions.  Here it is, the only part
you quoted:

> But, as the docs have always pointed out, it (specifically .fromutc(),
> which is at the base of all relevant calculations) doesn't even try to
> handle transitions due to _other_ causes.  The only other such cause
> I'm aware of is when a timezone's _base_ offset from UTC changes (not
> a temporary DST transition, the timezone's "standard" offset changes
> permanently (meaning until someone decides to change it again)).

Now you chide me with "And then you start discussing conversions,
which wasn't the issue, it
was arithmetic"?!  The quote you were replying to was _entirely_ about
conversions, and nothing whatsoever about arithmetic.  Silly me - I
thought you were asking about DST conversions and base-offset-changing
conversions.  And just because that was the topic you were commenting
on ;-)

Here's you. talking about conversion when the base UTC offset changes:

> This will be handled in the exact same way as DST changes, and if
> this is incorrect, then reasonably, so is the DST handling.
> What is "incorrect" here is of course a matter of opinion.

That's wholly consistent with the belief that you were staying on the
original topic (conversion).

Then you continued, I _guess_ talking about arithmetic, because you
weren't explicit and it really had nothing to do with the paragraph
just ended:

> I think  it's incorrect because it doesn't agree with reality, you have
> claimed that it is correct, in "as per design".

You weren't explicit about what "it" and "it's" referred to.  I
charitably tried to assume you weren't trying to change the current
topic (which _was_ conversions, and obviously so)., so replied at
length about how arithmetic and conversions were distinct issues.

Finally,

> But then reasonably that goes for this case as well? The same thing
> happens, which is that depending on the transitions direction, you can
> either end up in a time that doesn't exist, or one that happens twice.

Which seemed to be bouncing back to the original topic.  Or not.

Since you seem to believe _I_ was changing the topic, my best guess
now is that, without saying anything explicit about it, in your _head_
you weren't thinking about conversions at all, but instead about what
happens when doing _arithmetic_ at times near timezone transition
points.

If so, I plead guilty to a failure of telepathy ;-)

But the quote you responded to at first wasn't about arithmetic.  It
was about conversions.  In its original context that was dead obvious.
But even stripped of context, it still explicitly talks about
.fromutc().  A conversion method.  Not arithmetic.