Greetings,
I have noticed glibc's it_IT locale has quite a few mistakes:

-   Abbreviated and Full week days (e.g. Monday/Lunedì) do not have a capital letter (should be Lunedì but it is lunedì)
-   Abbreviated and Full months have the same problem as above, e.g. gennaio should be Gennaio
-   Language name (lang_name) still has the same problem as above (italiano instead of Italiano)

This bug is not present in other locales, as far as I know.
Latest source check date: 02/12/2021 @ 10:45
Version found in version.h: "2.34.9000" (development)

I have made the following patch: fix-italian.patch (you can find it in the attachments)
Here's a preview:
[patch.png]