[Datetime-SIG] Local time disambiguation proposal

[Chris Barker]

On Thu, Jul 30, 2015 at 11:33 AM, Alexander Belopolsky <
alexander.belopolsky at gmail.com> wrote:

> I have no emotional attachment to any particular name.


The intent is for this new flag to be used for that ambiguous time period
during the DST transitions.

However, at least in theory, it COULD be used for any time -- i.e. I was US
Eastern Standard Time, even though it's the middle of the summer. WHat a
user should do is use a tzinfo object that is specifically the Easter Time
zone offset, with no DST. (is this spelled "EST" or something in the Olsen
database?).

But we need to (a) be really clear in the docs whether the flag is
consulted any any other time. and (b) probably be really careful in the
code to make sure the flag is set appropriately at all times.

and, in this case, using a name like "is_dst" would imply to me that you
could turn DST on or off at any time. Whereas .is_first would mean nothing
to me at a glance, so I'd go read the docs, and hopefully get a nice
explanation ;-)

-Chris







If you like
> "is_first" better than "first" on the grammatical grounds - I have no
> problem changing the spelling.
>
> I do have two problems with calling it isdst:
>
> 1. Whether we want to implement the POSIX standard or not, but
> tm_isdst member is the POSIX solution to the problem at hand and if we
> give datetime objects a member variable called isdst, but change the
> semantics, we will see no end of bug reports.  (And since no one
> understands POSIX semantics, we have no choice but to change them. :-)
>
> 2. It will be very confusing to have t.is_dst ≠ t.dst()  which will
> happen whenever you have an ambiguity due to a change in the standard
> time.
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