<p>Does anyone know what this means. Getting this in C# winforms applications:</p>

<blockquote>
  <p>Not a legal OleAut date</p>
</blockquote>

It means you provided an invalid date somewhere, attempting to convert to or from an OLE Automation date outside the valid range 1-January-4713 BC to 31-December-9999 AD.  A possible cause is that it might have slipped through because OLE Automation Dates are represented as a double.