title: Reading Date from Excel File using OpenXML
body: <p>I'm making a library that uses OpenXML in C# to read excel files. I can read a cell text and numbers just fine, but when it comes to dates there's a problem. 
  There's the type "date" for the cells, but apparently Excel 2007 doesn't save the dates in that type, so I can't tell if the value I'm reading is a date or not, instead it appears to use styles.</p>
  
  <p>How could I detect if it is a date and return the string representation of it (ex: 29-12-2010)?</p>