Inconsistent behavior of datetime.strftime

[mouchen626]

Bug report

Bug description:

The datetime.strftime("%1") format specifier produces different results on Windows and Linux. This discrepancy may cause unexpected behavior in cross-platform applications.

from datetime import datetime
dt = datetime.now()
s = dt.strftime("%1")
print(s)

Windows: Raises an ValueError.
Linux: Returns "%1".

CPython versions tested on:

3.11

Operating systems tested on:

No response

[brianschubert]

The behavior of strftime is dependent on the C standard library implementation that Python links with. It’s known and documented that this can vary between platforms. Quoting the docs:

The full set of format codes supported varies across platforms, because Python calls the platform C library’s strftime() function, and platform variations are common. To see the full set of format codes supported on your platform, consult the strftime(3) documentation. There are also differences between platforms in handling of unsupported format specifiers.

[StanFromIreland]

This should be closed as not planned, it is correct as per the docs (quoted above).