title: datetime issue with xlrd & xlwt python libs
body: <p>I'm trying to write some dates from one excel spreadsheet to another. Currently, I'm getting a representation in excel that isn't quite what I want such as this: "40299.2501157407"</p>
  
  <p>I can get the date to print out fine to the console, however it doesn't seem to work right writing to the excel spreadsheet -- the data must be a date type in excel, I can't have a text version of it.</p>
  
  <p>Here's the line that reads the date in:</p>
  
  <pre><code>date_ccr = xldate_as_tuple(sheet_ccr.cell(row_ccr_index, 9).value, book_ccr.datemode)
  </code></pre>
  
  <p>Here's the line that writes the date out:</p>
  
  <pre><code>row.set_cell_date(11, datetime(*date_ccr))
  </code></pre>
  
  <p>There isn't anything being done to date_ccr in between those two lines other than a few comparisons.</p>
  
  <p>Any ideas?</p>