You can extend the life of a cookie beyond the current browser session by setting an expiration date and saving the expiry date within the cookie. This can be done by setting the ‘expires’ attribute to a date and time.
Example
You can try to run the following example to set cookies to expire in 30 minutes
Live Demo
<html>
<head>
<script>
<!--
function WriteCookie() {
var now = new Date();
var minutes = 30;
now.setTime(now.getTime() + (minutes * 60 * 1000));
cookievalue = escape(document.myform.customer.value) + ";"
document.cookie="name=" + cookievalue;
document.cookie = "expires=" + now.toUTCString() + ";"
document.write ("Setting Cookies : " + "name=" + cookievalue );
}
//-->
</script>
</head>
<body>
<form name="myform" action="">
Enter name: <input type="text" name="customer"/>
<input type="button" value="Set Cookie" onclick="WriteCookie()"/>
</form>
</body>
</html>