It bums me out to see warnings like this in the Python documentation:

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.

One of the benefits of a cross-platform high-level language like Python should be that it insulates you from these kinds of vagaries. Unless a function comes from the os module it should work the same whether it’s running on macOS, BSD, or a 5 MB Alpine Linux Docker container.