function isValidDate(strDate) {
     // (\d{1,2}) means 4 or 12
     // (\/|-) means either (/ or -), 4-12 or 4/12 
     // NOTE: we have to escape / (\/)
     // or else pattern matching will interpret it to mean the end instead of the literal "/"
     // \2 use the 2nd placeholder (\/|-) "here"
     // (\d{2}|\d{4}) means 02 or 2002
     var datePat = /^(\d{1,2})(\/|-)(\d{1,2})\2(\d{2}|\d{4})$/;
     var matchArray = strDate.match(datePat);

     if (matchArray == null) return false;

     // matchArray[0] will be the original entire string, for example, 4-12-02 or 4/12/2002
     var month = matchArray[1];     // (\d{1,2}) - 1st parenthesis set - 4
     var day = matchArray[3];         // (\d{1,2}) - 3rd parenthesis set - 12
     var year = matchArray[4];        // (\d{2}|\d{4}) - 5th parenthesis set - 02 or 2002

     if (month < 1 || month > 12) return false;
     if (day < 1 || day > 31) return false;
     if ((month == 4 || month == 6 || month==9 || month == 11) && day == 31) return false;
     if (month == 2) {
          var isleap = (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0));

          if (day > 29 || (day == 29 && !isleap)) return false;
     }
     return true;
}