title: Regular Expression to detect yyyy-MM-dd
body: <p>I use asp.net 4 and c#.</p>
  
  <p>I need to use a WebControl of type Validation namely <code>RegularExpressionValidator</code> to detect data inputed in a TextBox that <code>IS NOT in format yyyy-MM-dd</code> (String).</p>
  
  <p>Any idea how to write the RegEx to apply ot this control?</p>
  
  <p>Thanks</p>