Some date formats get incorrectly output in Italian

[Clorith]

When using the date format l j F Y (Monday 11 November 2019), and changing the site language to Italian, the output becomes "Lundeì 11 20 Novembre 19", essentially embracing the month with the year.

This output shows up in the preview in wp-admin when changing the format, and in the front end, for example the date display in Twenty Twenty above posts.

The behavior changed with the 5.3 release, and I've so far only had reports and replicated this with Italian, but there may be other strange scenarios with other languages.

[Rarst]

I think this got broken by additions in wp_maybe_decline_date(), https://core.trac.wordpress.org/changeset/45555

There was unit test added for Russian with it, so the issue might be it not behaving right with another locale(s).

I didn't write the code, will look into it on fresh head.