Javascript - quarter start and end

gistfile1.js

var now = new Date();
var quarter = Math.floor((now.getMonth() / 3));
var firstDate = new Date(now.getFullYear(), quarter * 3, 1);
var endDate = new Date(firstDate.getFullYear(), firstDate.getMonth() + 3, 0);

<title>DateQuarter</title> Query

Dated:

<script src="http://code.jquery.com/jquery-latest.js"></script> <script> var isPostBack = false;

		function pageLoad()
		{
			if (isPostBack === false)
			{
				$.getScript("/WordEngineering/WordUnion/9432.js", function( data, textStatus, jqxhr ) 
				{
					var dated = scriptLiteral9432.getParameterByName("dated");
					if (!dated)
					{
						dated = scriptLiteral9432.todayTimezoneOffset();
					}	
					document.getElementById("dated").value = dated;

					querySubmit();
					
					isPostBack = true;	
				});
			}
		}
		
		function querySubmit()
		{
			var dated = new Date(document.getElementById("dated").value); 
			var quarter = Math.floor((dated.getMonth() / 3));
			var firstDate = new Date(dated.getFullYear(), quarter * 3, 1);
			var endDate = new Date(firstDate.getFullYear(), firstDate.getMonth() + 3, 0);

			var resultSet = "<table style='text-align: left;'>";
			resultSet += scriptLiteral9432.buildHead("Unit", "Value");
			resultSet += scriptLiteral9432.buildRow("Quarter", quarter + 1);
			resultSet += scriptLiteral9432.buildRow("First Date", firstDate);
			resultSet += scriptLiteral9432.buildRow("First Date", endDate);
			resultSet += "</table>";
			
			document.getElementById("resultSet").innerHTML = resultSet;
		}
		
		window.addEventListener("load", pageLoad, false);
		
		document.getElementById("dated").addEventListener("change", querySubmit, false);
		
		document.getElementById("submitQuery").addEventListener("click", querySubmit, false);
		
		var body = document.getElementsByTagName('body')[0];
		body.onkeydown = function (e) {
			if (e.keyCode === 13) {  //enter key code
				loadDoc();
			}
		}
	</script>
</body>