Для тех, кто не хочет использовать метод datepicker
var alldatepicker= $("[class$=hasDatepicker]");
alldatepicker.each(function(){
var value=$(this).val();
var today = new Date();
var dd = today.getDate();
var mm = today.getMonth()+1; //January is 0!
var yyyy = today.getFullYear();
if(dd<10) {
dd='0'+dd
}
if(mm<10) {
mm='0'+mm
}
today = mm+'/'+dd+'/'+yyyy;
if(value!=''){
if(value>today){
alert("Date cannot be greater than current date");
}
}
});