I am learning about Language Packs as fast as you.
Changing the Date Format works in the default English version of Text Schemes but has no effect (except for Year) when a different Output Language is chosen.
The explanation is that the Date formatting is performed by the Language Pack Plugin and the default plugin ignores the Date Format qualifiers.
I will ask CP if that can be improved.
It is also the Language Pack Plugin that determines the translation of words such as ‘between’, ‘and’, ‘from’ & ‘to’ in Dates.
Use Tools > Language Packs… select Slovenian and click Plugin… to edit the plugin script where every << TODO marker appears.
sHusband = '(no name)'; -- << TODO Replace (no name) with the Slovenian equivalent words.
sText = "between " .. GetDatePtText(date:GetDatePt1(), "", "") .. " and " .. GetDatePtText(date:GetDatePt2(), "", ""); -- << TODO Replace "between " and " and " with the Slovenian equivalent words.
You can also force the dd.mm.yyyy format in this plugin.
Near line number 630 you will find: function GetDatePtText(datept, sPrefix1, sPrefix2)
That needs these subsequent two lines to be replaced at about line numbers 642 and 646:
sDay = iDay .. ' '; becomes sDay = iDay .. '.';
sMonth = g_months[iMonth] .. ' '; becomes sMonth = iMonth .. '.';
Be very careful not to change the layout of the script, especially the symbols, otherwise it won’t work.
As the Help advises, save a plain text copy of the plugin script file as a backup just in case.