This isn't a workaround, but does address the Excel date format conundrum when processing a .xls file with PHP and PHPExcel, where the cell is formatted [$-409]YYYY-MM-DD;@.
Since OO doesn't preserve the date cell value as human readable text in an .xls, I found out how PHP can convert it.
$EXCEL_DATE=42349.6189117708;
$UNIX_DATE = ($EXCEL_DATE - 25569) * 86400;
echo 'Excel gmdate test ' . gmdate("Y-m-d", $UNIX_DATE);
Excel gmdate test 2015-12-11
Works for me. (See screen cap above for the date on the Amazon .xls cell, and the cell format.)
http://stackoverflow.com/questions/1111 ... -php-excel <- didn't find it on the first Google!  Explanation is enlightening, in regards to differences between *NIX and MS dates.
This technique does not address other instances of OO flipping a cell format from Text to number for UPC/ISBN or other date data entries, especially strings of numeric characters separated with '/'s.
 
			
			
									
						
							Open Office 4 on OS X El Capitan.