how to fix the error "String was not recognized as a valid DateTime."

function isDate(txtDate) {
               var currVal = txtDate;
               if (currVal == '')
                   return false;

               //Declare Regex
               var rxDatePattern = /^(\d{1,2})(\/|-)(\d{1,2})(\/|-)(\d{4})$/;
               var dtArray = currVal.match(rxDatePattern); // is format OK?

               if (dtArray == null)
                   return false;

               //Checks for mm/dd/yyyy format.
               dtDay = dtArray[1];
               dtMonth = dtArray[3];
               dtYear = dtArray[5];

               if (dtMonth < 1 || dtMonth > 12)
                   return false;
               else if (dtDay < 1 || dtDay > 31)
                   return false;
               else if ((dtMonth == 4 || dtMonth == 6 || dtMonth == 9 || dtMonth == 11) && dtDay == 31)
                   return false;
               else if (dtMonth == 2) {
                   var isleap = (dtYear % 4 == 0 && (dtYear % 100 != 0 || dtYear % 400 == 0));
                   if (dtDay > 29 || (dtDay == 29 && !isleap))
                       return false;
               }

if ($('#txtLoanDate').val() != '' && !isDate($('#txtLoanDate').val())) {
                    alert("EMI date must be in DD/MM/YY Format ");
                    return false;
                }