Some features are documented as "Proprietary extension", but that doesn't see true

Hi there,

In the docs I read that some date-formatting features (format characters f, P, and N) are flagged as “Proprietary extensions”. Is this still true? Of course this is auto-generated docs, so by blaming the source file utils/dateformat.py, I see that these docstrings haven’t been changed for more than a decade.

This may be confusing for some users, and maybe some of them don’t use these formatting options because of that…

So if these formatting options are really not proprietary, I would be happy to open a PR to remove these affirmations from the docs.

Thanks

I think this is to be read in the full context of those docs, in that those “proprietary “ codes either don’t exist in php or have a different meaning as shown at PHP: DateTimeInterface::format - Manual