I am opening this issue because I saw on a blog (http://lingonborough.com/fedora-28-updates-for-czech-catalan-greek-and-lithuanian-users/) that improvements had been made for the date format in Catalan.
The changes made for Catalan can apply to Occitan too, we also use the preposition DE before months, an D’ before April (abrial), August (agost) and October (octòbre).
I created files for gblibc that can be found here:
There you get all the information to display correctly the date in Occitan, based on the Catalan experience.
What should I do to spread the correct format all around?