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

Chris Barker chris.barker at noaa.gov
Wed Aug 19 22:54:19 CEST 2015

On Wed, Aug 19, 2015 at 1:30 PM, Carl Meyer <carl at oddbird.net> wrote:

> > I don't have the official $300+ PDF of the standard

neither do I :-(

> , but wikipedia
> > disagrees with you:
> > <https://en.wikipedia.org/wiki/ISO_8601#Time_zone_designators>.
> I think Chris is distinguishing between "timezones" and "UTC offsets".
> ISO 8601 can certainly encode a UTC offset, but it can't encode a
> timezone in the sense of "America/New_York".

exactly. However, the Wikipedia page does say:

"Time zones <https://en.wikipedia.org/wiki/Time_zone> in ISO 8601 are
represented as local time (with the location unspecified), as UTC
<https://en.wikipedia.org/wiki/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.

but it's not reliable to reverse-engineer and offset to find the timezone.

though I don't think this really has anything to do with the topic at ahnd
-- is anyone proposing that parsing ISO strings _should_ assume a time zone?

BTW, an ISO string without an offset (or z, or...) is often (officially)
called "local time". So numpy's datetime takes that to mean the timezone of
the machine's locale settings -- which is a really ugly mess, so let's not
do that.



Christopher Barker, Ph.D.

Emergency Response Division
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Chris.Barker at noaa.gov
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