It seems that the parser is lax when it comes to parsing against a format. For example, if you specify EEEE for the day of the week, the parser is expecting a full week-day name (eg. "Monday"). However, if the short form is found (eg. "Mon", represented by EEE), it is parsed without error. If this is the behavior we want for the parser (assuming the smart parsing is actually smart and without error), the spec/requirements likely need to be updated in this area, particularly DFDL-13-153R, which states "The count of pattern letters determines the format."