DateAdapter.java

private static SimpleDateFormat format=new SimpleDateFormat("yyyy-MM-dd");

    ...

@Override
public XMLGregorianCalendar unmarshal(String value)throws Exception {

    ...
    Date date=format.parse(value);
    GregorianCalendar calendar=new GregorianCalendar();
    calendar.setTime(date);
    return DatatypeFactory.newInstance().newXMLGregorianCalendar(calendar);
    ...
}

@Override
public String marshal(XMLGregorianCalendar value)throws Exception {
    return format.format(value.toGregorianCalendar().getTime());
}