myscript.js

var userMonth = document.getElementById("user-month");
var userDay = document.getElementById("user-day");
var userYear = document.getElementById("user-year");
var submitButton = document.getElementById("submit-date");

submitButton.addEventListener("click", function(evt) {
	var message = document.getElementById('message');
    var parsedMonth = (parseInt(userMonth.value)-1);
	var parsedDay = parseInt(userDay.value);
	var parsedYear = parseInt(userYear.value);

	var months = ["January","February","March","April","May","June","July","August","September","October","November","December"];
    var weekday = ["Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"];
    var dateIs = new Date(parsedYear, parsedMonth, parsedDay);
    var weekdayIs = weekday[dateIs.getDay()];
    var monthIs = months[parsedMonth];

    if (weekdayIs === undefined || monthIs === undefined) {
    	message.innerText= "";
    	setTimeout(function() {
    		message.innerText="Please enter a valid date!";}, 500)
    }
    else{
    	message.innerText = weekdayIs +" , "+ monthIs + " " + parsedDay + " , " +parsedYear;
    }

})