https://www.gedersdorf.at/system/statV.1789655742/Javascript/jquery/datepicker-de.js

1jQuery(function ($) {
2    $.datepicker.regional['de'] = {
3        closeText: 'schließen',
4        prevText: '<zurück',
5        nextText: 'Vor>',
6        currentText: 'heute',
7        monthNames: ['Januar', 'Februar', 'März', 'April', 'Mai', 'Juni',
8                     'Juli', 'August', 'September', 'Oktober', 'November', 'Dezember'],
9        monthNamesShort: ['Jan', 'Feb', 'Mär', 'Apr', 'Mai', 'Jun',
10                      'Jul', 'Aug', 'Sep', 'Okt', 'Nov', 'Dez'],
11        dayNames: ['Sonntag', 'Montag', 'Dienstag', 'Mittwoch', 'Donnerstag', 'Freitag', 'Samstag'],
12        dayNamesShort: ['So', 'Mo', 'Di', 'Mi', 'Do', 'Fr', 'Sa'],
13        dayNamesMin: ['So', 'Mo', 'Di', 'Mi', 'Do', 'Fr', 'Sa'],
14        weekHeader: 'Wo',
15        dateFormat: 'dd.mm.yy',
16        firstDay: 1,
17        isRTL: false,
18        showMonthAfterYear: false,
19        yearSuffix: '',
20        onClose: function (selectedDate, e) {
21            var curVal = e.input.val();
22            if (curVal != "") {
23                var matched = curVal.match(/^(0[1-9]|[12][0-9]|3[01])(0[1-9]|1[012])(19\d\d|20\d\d|\d\d)$/);
24                console.log(matched);
25                if (matched != null && matched.length == 4)
26                    e.input.val(matched[1] + "." + matched[2] + "." + (matched[3].length == 2 ? "20" : "") + matched[3]);
27            }
28        }
29    };
30
31    $.datepicker.setDefaults($.datepicker.regional['de']);
32});