locale = navigator.browserLanguage || navigator.language || navigator.userLanguage;

vai__#Latn---> 21/01/1970
ksb_TZ---> 21/01/1970
ksh---> 21. 1. 1970
ur_IN---> ??/?/??
ln---> 21/1/1970
en_JE---> 21/01/1970
gsw_CH---> 21.01.70
ln_CF---> 21/1/1970
en_CX---> 21/01/1970
luy_KE---> 21/01/1970
pt---> 21/01/1970
en_AT---> 21/01/1970
gl---> 21/01/70
kkj_CM---> 21/01 1970
sr__#Cyrl---> 21.1.70.
yue_CN_#Hans---> 1970/1/21
es_GQ---> 21/1/70
kn_IN---> 21/1/70
ar_YE---> ???/??/????
to---> 21/1/70
en_SX---> 21/01/1970
ga---> 21/01/1970
qu---> 21/01/1970
ru_KZ---> 21.01.1970
en_TZ---> 21/01/1970
et---> 21.01.70
en_PR---> 1/21/70
mua---> 21/1/1970
ko_KP---> 70. 1. 21.

        final String regex = "([^,\\s]{1,})(.{1,})";
        final Pattern pattern = Pattern.compile(regex, Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE);
        Locale[] locales = DateFormat.getAvailableLocales();
        for (Locale loc : locales) {
            String ss = String.format(loc, "%s",  ((SimpleDateFormat) DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.SHORT, loc)).toPattern());
            Matcher matcher = pattern.matcher(ss);
            if (matcher.find()) {
                System.out.println(loc.toString() + "\t\t  " + matcher.group(1));
            }
        }