[Datetime-SIG] PEP-0500 (Alternative datetime arithmetic) Was: PEP 495 ... is ready ...

Łukasz Rekucki lrekucki at gmail.com
Thu Aug 20 07:33:34 CEST 2015

On Thursday, August 20, 2015, Alexander Belopolsky <
alexander.belopolsky at gmail.com> wrote:

> On Wed, Aug 19, 2015 at 4:54 PM, Chris Barker <chris.barker at noaa.gov
> <javascript:_e(%7B%7D,'cvml','chris.barker at noaa.gov');>> wrote:
> >
> > However, the Wikipedia page does say:
> >
> > "Time zones in ISO 8601 are represented as local time (with the location
> unspecified), as UTC, or as an offset from UTC."
> >
> > but nothing about how one specifies the location -- I have no idea if
> there is an ISO 8601 way to specify a location, but I've never seen it --
> wikipedia may mean that it should be specified some other way than embedded
> in the string.
> Correct, but specifying the location has nothing to do with the computer
> notion of a time zone.   The IETF experts working on the Time Zone Data
> Distribution standard explain that right in the introduction:
>    Note that the term "time zone" does not have the common meaning of a
>    region of the world at a specific UTC offset, possibly modified by
>    daylight saving time.
You have read this totally backwards. The quote says that the time zone can
NOT be seen as a simple UTC offset +/-DST (which is a common misconception
that can be seen on many "timezone" maps). As an example CET is given -
it's not a timezone as it consist of "Europe/Warsaw", "Europe/Berlin", etc.

>From datetime implementation perspective Tim's definition is the best, but
from perspective of a implementing a timezone database a thing like CET or
-0500 is just ambiguous because it means one of many actuall timezones.

Łukasz Rekucki
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