The ISDATE program determines whether a text expression represents a valid date. ISDATE only tests a text expression to see if it can be converted to a DATE-only value; it does not actually make the conversion. You must use CONVERT to make the conversion.
YES when the text expression represents a valid date;
NO when it does not.
A single-line ID or TEXT expression to be examined to see if it represents a valid date, as defined by the DATE-only data type. For a description of the valid styles for entering dates, see "Date-only Input Values".