[Python-Dev] Status on PEP-431 Timezones

[Lennart Regebro]

On Sat, Jul 25, 2015 at 7:12 AM, Tim Peters <tim.peters at gmail.com> wrote:
> [Lennart Regebro <regebro at gmail.com>]
>> And I would want to remind everyone again that this is not a question
>> of the problem being impossible. It's just really complex to get right
>> in all cases, and that always having the UTC timestamp around gets rid
>> of most of that complexity.
>
> Could you please be explicit about what "the problem" is?  Everyone
> here is guessing at what you think "the problem" is.

The problem is that it is exceedingly complicated to get all the
calculations back and forth between local time and UTC to be correct
at all times and for all cases. It really doesn't get more specific
than that. I don't remember which exact problem it was that made me
decide that this was not the correct solution and that we should use
UTC internally, but I don't think that matters, because I'm also sure
that it was not the last case, as I was far from near the end in
adding testcases.

Once again I'm sure it's not impossible to somehow come up with an
implementation and an API that can do this based on local time, but
once again I am of the opinion that it is the wrong thing to do. We
should switch to using UTC internally, because that will make
everything so much simpler.

I am in no way against other people implementing this PEP, but I think
you will end up with very complex code that will be hard to maintain.

There really is a reason every other date time implementation I know
of uses UTC internally, and there really is a reason why everyone
always recommends storing date times in UTC with the time zone or
offset separately.

//Lennart