strptime not parsing some timezones

[utkonos]

BPO	25963
Nosy	@abalkin, @bitdancer, @vadmium, @Fidget-Spinner, @akulakov

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2021-09-07.15:34:06.320>
created_at = <Date 2015-12-28.08:32:13.256>
labels = ['type-bug', '3.9', 'docs']
title = 'strptime not parsing some timezones'
updated_at = <Date 2021-09-07.15:34:06.317>
user = 'https://bugs.python.org/utkonos'

bugs.python.org fields:

activity = <Date 2021-09-07.15:34:06.317>
actor = 'andrei.avk'
assignee = 'docs@python'
closed = True
closed_date = <Date 2021-09-07.15:34:06.320>
closer = 'andrei.avk'
components = ['Documentation']
creation = <Date 2015-12-28.08:32:13.256>
creator = 'utkonos'
dependencies = []
files = []
hgrepos = []
issue_num = 25963
keywords = []
message_count = 5.0
messages = ['257108', '257262', '257294', '399153', '401293']
nosy_count = 7.0
nosy_names = ['belopolsky', 'r.david.murray', 'docs@python', 'martin.panter', 'utkonos', 'kj', 'andrei.avk']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue25963'
versions = ['Python 3.9']

[utkonos]

I get a ValueError when running the following through strptime:

datetime.datetime.strptime('(CST)', '(%Z)')

But the following works:
datetime.datetime.strptime('(EST)', '(%Z)')

PST and MST also trigger the same exception.

[vadmium]

I suspect the datetime module’s %Z parsing depends on the locale, just like time.strptime() does: <https://docs.python.org/dev/library/time.html#time.strptime\>.

[bitdancer]

The code is shared by the two modules (it's in _strptime.py). So, yes.

There is clearly a doc bug here (%Z needs a footnote in the table in the datetime docs), but there is no practical way to implement the parsing of arbitrary (non-locale) timezone strings, since it is not a one-to-one mapping.

[akulakov]

This was fixed so can be closed.

Current datetime docs have a footnote for %Z:

...
strptime() only accepts certain values for %Z:

any value in time.tzname for your machine’s locale

the hard-coded values UTC and GMT

[akulakov]

I'm closing this as fixed, the note in datetime docs is here:

https://docs.python.org/3.9/library/datetime.html

(search for 'only accepts', - note 6)