gistfile1.js

function validateDateFormat(dateValue) {
  var dateRegex = /^(\d{2})\/(\d{2})\/(\d{4})$/;
  var dateOK = true;

  if (!dateValue.blank() ) {
    if(!dateRegex.test(dateValue)) {
      dateOK = false;
    } else {
      var d = new Date(dateValue.replace(dateRegex, '$2/$1/$3'));
      var ok = ( parseInt(RegExp.$2, 10) == (1+d.getMonth()) ) && 
        (parseInt(RegExp.$1, 10) == d.getDate()) && 
        (parseInt(RegExp.$3, 10) == d.getFullYear() ) ;
      if (!ok) { dateOK = false; }
    } 
  }
  
  return dateOK;
}