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 = new StringFormatter( pattern ).format( string );
			}
		}
		catch ( BirtException e )
		{
			
		}
		catch ( ParseException e )
		{
		}
		return string;
	}
	/**
	 * Check if the specified value is valid
	 * 
	 * @param value
	 *            the value to check
	 * @return Returns the error message if the input value is invalid,or null
	 *         if it is valid
	 */
	private String isValidValue( String value )
	{
		if ( canBeNull( ) )
		{
			if ( value == null || value.length( ) == 0 )
			{
				return null;
			}
		}
		else