Develop

Modified DateWidget to handle Excel date format. add a private method to class DateWidget(Widget)

    def __xldate_as_datetime(self, xldate, datemode=0):
        # datemode: 0 for 1900-based, 1 for 1904-based
        return (datetime(1899, 12, 30) +
                timedelta(days=xldate + 1462 * datemode)).date()