Bug 118644 Hint for Date Time Parameters
The hint you give for date time parameters (Please enter date ... pattern: MM/DD/YYYY ....) is only true if the date is unformatted. If you apply a format, you must enter it according to it. So it's quite confusing!
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/ParameterDialog.java
String value = null;
			if ( COLUMN_VALUE.equals( property ) )
			{
				value = choice.getValue( );
			}
			else if ( COLUMN_DISPLAY_TEXT.equals( property ) )
			{
				value = choice.getLabel( );
			}
			if ( value == null )
			{
				value = ""; 
			}
			return value;
		}
		public void modify( Object element, String property, Object value )
		{
			if ( element instanceof Item )
			{
				element = ( (Item) element ).getData( );
			}
			SelectionChoice choice = ( (SelectionChoice) element );