Hey there,
Thanks for the report. I can see how the Js that check date format may fail with utf8 characters. We'll do our best to resolve the issue, but I can't promise it'll make it to the next release.
Feel free to locally edit file modules/Utils/PopupCalendar/datepicker.js, lines 14-17 and 22-25
if(!this.re.test(elem.value)) {
alert('Invalid date - clearing');
elem.value='';
}
simply comment or remove them.
Kind regards,
Arek
