code: private boolean isDateTime(long style)
      {
          boolean ret = false;
  
          if(style > 0L)
          {
              CTXf xf = workbook.getStylesheet().getCellXfs().getXf().get((int)style);
              long numFmtId = 0L;
              if(xf.getNumFmtId() != null)
                  numFmtId = xf.getNumFmtId().longValue();
              if(numFmtId < 164)
              {
                  ret = (numFmtId >= 14 && numFmtId <= 22) 
                      || numFmtId == 30 
                      || (numFmtId >= 45 && numFmtId <= 47);
              }
              else
              {
                  String formatCode = workbook.getFormatCode(numFmtId);
                  if(formatCode != null)
                  {
                      ret = formatCode.indexOf("h:mm") != -1;
                  }
              }
          }
  
          return ret;
      }
docs: Returns <CODE>true</CODE> if the given style ref is a date or time.
  <P>
  The following formats are supported:
  14 = 'mm-dd-yy'
  15 = 'd-mmm-yy'
  16 = 'd-mmm'
  17 = 'mmm-yy'
  18 = 'h:mm AM/PM'
  19 = 'h:mm:ss AM/PM'
  20 = 'h:mm'
  21 = 'h:mm:ss'
  22 = 'm/d/yy h:mm'
  30 = 'm/d/yy'
  45 = 'mm:ss'
  46 = '[h]:mm:ss'
  47 = 'mmss.0'
  @param style The style reference
  @return <CODE>true</CODE> if the given style ref is a date or time