pearu commented on PR #50146:
URL: https://github.com/apache/arrow/pull/50146#issuecomment-4668970610

   CI triage of the first run (3 failing jobs, all Windows): all three shared 
one root cause — the tests used the `%d-%b-%y` format from the original issue 
reproducer, but **month names (`%b`) are not supported by the vendored musl 
`strptime` used on Windows**: `cpp/src/arrow/vendored/musl/strptime.c` 
force-undefines `HAVE_LANGINFO` on `_WIN32`, which compiles out the 
`%a`/`%A`/`%b`/`%B`/`%h`/`%c`/`%p`/`%r`/`%x`/`%X` cases entirely. The feature 
code is unaffected; numeric-format and time tests passed on Windows.
   
   Fixed (amended) by making numeric formats the primary test coverage and 
keeping the month-name reproducer guarded to non-Windows (`#ifndef _WIN32` in 
C++, `sys.platform != "win32"` in Python, following the existing 
`kStrptimeSupportsZone` / `test_strftime` precedents).
   
   A third discovery for the list above: this `%b` limitation is pre-existing 
and applies equally to `timestamp` columns with `timestamp_parsers` on Windows 
— it just had no CI coverage because the existing timestamp tests only use 
numeric formats. Could deserve its own issue (either implementing C-locale 
month names in the vendored strptime, or documenting the limitation in 
`timestamp_parsers` docs).


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