This closes #10453

PR Summary

One missing digit in a comment

        fmt = fmt.replace("%s", "s")
        if dt.year >= 1900:
            # Note: in python 3.3 this is okay for years >= 1000,
            # refer to http://bugs.python.org/issue177742
            return cbook.unicode_safe(dt.strftime(fmt))

should be http://bugs.python.org/issue1777412

(Suggested by @jenshnielsen and confirmed in #3242 (comment))

PR Checklist

• Has Pytest style unit tests
• Code is PEP 8 compliant
• New features are documented, with examples if plot related
• Documentation is sphinx and numpydoc compliant
• Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
• Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way

(no new feature, no major change, no API change, didn't check the others but
given how minor the change is I expect what was PEP8, shinx and numpydoc
compliant should stay so)