If I google for "Unable to convert MySQL date/time value to System.DateTime" I see numerous references to a problem accessing MySQL from Visual Studio. Is that your context?
One solution suggested is:
This is not a bug but expected behavior. Please check manual under connect options and set "Allow Zero Datetime" to true, as on attached pictures, and the error will go away.
Reference: http://bugs.mysql.com/bug.php?id=26054