`time.strftime` does't work properly with format specifier `%f` on Windows

[igor-sadchenko]

When using the time.strftime() function with the format string "%Y-%m-%dT%H:%M:%S.%f000Z" on Windows, the %f specifier for microseconds does not work as expected. The same format works correctly on Linux and macOS.

Example code:

import time
time.strftime("%Y-%m-%dT%H:%M:%S.%fZ", time.gmtime())

Expected behavior:

The %f specifier should return the microsecond part of the time when used in the time.strftime() format string, similar to how it works on Linux and macOS.

Example output on Linux/macOS:

2024-09-06T14:53:10.123000Z

Actual behavior on Windows:

On Windows, the %f specifier is not recognized by time.strftime(), and no microseconds are included in the output.

Example output on Windows:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: Invalid format string

Platform Information:

• OS: Windows 10 (also tested on other Windows versions)
• Python version: Affected on Python 3.x (tested on Python 3.8, 3.9, 3.10, 3.11, 3.12)

Additional information:

• The %f specifier seems to work correctly on Unix-based systems (Linux/macOS).
• The issue might be related to how the Windows implementation of time.strftime() interacts with the underlying system libraries.
• This is inconsistent behavior across different platforms, and it would be ideal for %f to work consistently.

CPython versions tested on:

3.8, 3.9, 3.10, 3.11, 3.12

Operating systems tested on:

Linux, macOS, Windows

[picnixz]

I'm surprised that it actually works on Linux/Darwin because the docs are clear for this: https://docs.python.org/3.13/library/time.html#time.strftime

The %f format directive only applies to strptime(), not to strftime(). However, see also datetime.datetime.strptime() and datetime.datetime.strftime() where the %f format directive applies to microseconds.

By the way, it does not work on (some) Linux platforms (mine is openSUSE with GCC 7.5):

>>> import time
... time.strftime("%Y-%m-%dT%H:%M:%S.%fZ", time.gmtime())
...
'2024-09-06T15:09:14.%fZ'

In addition:

Additional directives may be supported on certain platforms, but only the ones listed here have a meaning standardized by ANSI C. To see the full set of format codes supported on your platform, consult the strftime(3) documentation.

[picnixz]

Closing as not planned since the OP did not reply and the behaviour is documented.