18 May
2010
18 May
'10
7:20 p.m.
I think Roman numbers should be displayed as upper case roman number, at least when they are part of a ref or name. If you have always seen a street name as, say "Juan XXIII" it may be difficult to recognize it as "Juan 23". For dates it could be better to translate into Arabic numbers as you propose.
Yes, its my opinion too. Don't try to transliterate roman numbers. If in the database are entered roman numbers, somone has done it by intention. If this is really wrong, then correct the database.