Javascript code not showing any alert dialog

<html>
<head>

<title>BD Home page</title>

<style>
    body{background-color:red;}
    p{background-color:yellow;}
    div{background-color:green; }
</style>

</head>

<body>
<script>
function mf()
{
    Var x=new Date();
    alert("Today is: "+x);
}
</script>
<button onclick="mf()">Click</button>
<div>Hellllllooooo</div>
<p>Hello this is html</p>

</body>
</html>

Hello i am a begier programmer.In the error code it says mf in not defined on line 1:1, caot understand that Is it important to enclose an alert dialog box under a function ?