[ARROW-15884] [C++][Doc] Document that the strptime kernel ignores %Z

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: C++, Documentation
• Labels: good-first-issue kernel
• External issue URL: https://github.com/apache/arrow/issues/31315
• Assignee: Unassigned
• Reporter: Joris Van den Bossche
• Created: 09/Mar/22 13:49
• Updated: 11/Jan/23 11:40

Description

After ARROW-12820, the strptime kernel still ignores the %Z specifier (for timezone names), and when using it, it basically ignores any string.

For example:

# the %z specifier now works (after ARROW-12820)
>>> pc.strptime(["2022-03-05 09:00:00+01"], format="%Y-%m-%d %H:%M:%S%z", unit="us")
<pyarrow.lib.TimestampArray object at 0x7f00c1dd21c0>
[
  2022-03-05 08:00:00.000000
]

# in theory this should give the same result, but %Z is still ignore
>>> pc.strptime(["2022-03-05 09:00:00 CET"], format="%Y-%m-%d %H:%M:%S %Z", unit="us")
<pyarrow.lib.TimestampArray object at 0x7f00c86d1ca0>
[
  2022-03-05 09:00:00.000000
]

# as a result any garbage in the string is also ignored
>>> pc.strptime(["2022-03-05 09:00:00 blabla"], format="%Y-%m-%d %H:%M:%S %Z", unit="us")
<pyarrow.lib.TimestampArray object at 0x7f00c1db1ca0>
[
  2022-03-05 09:00:00.000000
]

I don't think it is easy to actually fix this (at least as long as we use the system strptime, see also https://github.com/apache/arrow/pull/11358#issue-1020404727). But at least we should document this limitation / gotcha.

Issue Links

• is a child of: ARROW-15894 [C++] Strptime issues umbrella
• is related to: ARROW-12820 [C++] Strptime ignores timezone information