title: What indicates an Office Open XML Cell contains a Date/Time value?
body: <p>I'm reading an .xlsx file using the <a href="http://www.microsoft.com/downloads/en/details.aspx?FamilyId=C6E744E5-36E9-45F5-8D8C-331DF206E0D0&amp;displaylang=en" rel="noreferrer">Office Open XML SDK</a> and am confused about reading Date/Time values.  One of my spreadsheets has this markup (generated by Excel 2010)</p>
  
  <pre><code>&lt;x:row r="2" spans="1:22" xmlns:x="http://schemas.openxmlformats.org/spreadsheetml/2006/main"&gt;
    &lt;x:c r="A2" t="s"&gt;
      &lt;x:v&gt;56&lt;/x:v&gt;
    &lt;/x:c&gt;
    &lt;x:c r="B2" t="s"&gt;
      &lt;x:v&gt;64&lt;/x:v&gt;
    &lt;/x:c&gt;
    .
    .
    .
    &lt;x:c r="J2" s="9"&gt;
      &lt;x:v&gt;17145&lt;/x:v&gt;
    &lt;/x:c&gt;
  </code></pre>
  
  <p>Cell J2 has a date serial value in it and a style attribute <code>s="9"</code>.  However, the Office Open XML Specification says that 9 corresponds to a followed hyperlink.  This is a screen shot from page 4,999 of <em>ECMA-376, Second Edition, Part 1 - Fundamentals And Markup Language Reference.pdf</em>.</p>
  
  <p><img src="https://i.stack.imgur.com/s9bnI.png" alt="alt text"></p>
  
  <p>The presetCellStyles.xml file included with the spec also refers to <code>builtinId</code> 9 as a followed hyperlink.</p>
  
  <pre><code>&lt;followedHyperlink builtinId="9"&gt;
  </code></pre>
  
  <p>All of the styles in the spec are simply visual formatting styles, not number styles.  Where are the number styles defined and how does one differentiate a style reference <code>s="9"</code> from indicating a cell formatting (visual) style vs a number style?</p>
  
  <p>Obviously I'm looking in the wrong place to match styles on cells with their number formats.  Where's the right place to find this information?</p>