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

Alexander Belopolsky alexander.belopolsky at gmail.com
Thu Aug 20 16:53:17 CEST 2015

On Thu, Aug 20, 2015 at 1:33 AM, Łukasz Rekucki <lrekucki at gmail.com> wrote:
> 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.

By your logic, UTC is not a time zone either because it "counsists of"
Europe/London, Africa/Casablanca etc.   This is a very unorthodox point of

> 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.

Whatever your definition of "actual timezone" is, if you want to use Python
effectively you need to understand the terms as they are used in the
library manual.  And there we have, for example: "%Z - Time zone name
(empty string if the object is naive) - (empty), UTC, EST, CST", [1] "%Z -
Time zone name (no characters if no time zone exists), " [2] "tm_zone -
abbreviation of timezone name," [3]  "time.tzname - A tuple of two strings:
the first is the name of the local non-DST timezone, the second is the name
of the local DST timezone." [4] and so on.

You can insist that CET is not a timezone as much as that 0 is not a
number, but as far as Python timekeeping goes, timezone is whatever Tim
says it is.  (Those who disagree can think of Python timezones as
TIMezones. :-)

[2]: https://docs.python.org/3/library/time.html#time.strftime
[3]: https://docs.python.org/3/library/time.html#time.struct_time
[4]: https://docs.python.org/3/library/time.html#time.tzname
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