private String getFormattedDateString(Double data, Short dataFormat, String dataFormatString) {
        Format dateFormat = getFormat(data, dataFormat, dataFormatString);
        if (dateFormat instanceof ExcelStyleDateFormatter) {
            // Hint about the raw excel value
            ((ExcelStyleDateFormatter)dateFormat).setDateToBeFormatted(data);
        }
        return performDateFormatting(DateUtils.getJavaDate(data, use1904windowing), dateFormat);
    }
Returns the formatted value of an Excel date as a <tt>String</tt> based on the cell's <code>DataFormat</code>.
i.e. "Thursday, January 02, 2003" , "01/02/2003" , "02-Jan" , etc.
<p>
If any conditional format rules apply, the highest priority with a number format is used. If no rules contain a
number format, or no rules apply, the cell's style format is used. If the style does not have a format, the
default date format is applied.

@param data             to format
@param dataFormat
@param dataFormatString
@return Formatted value
fastexcel-core/src/main/java/cn/idev/excel/metadata/format/DataFormatter.java