index.html

<!DOCTYPE html> 
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no">
    <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Rubik+Mono+One|Lilita+One">
    <link rel="manifest" href="app.json" />
    <title>Age</title>
    <style>
        *{
            user-select: none;
            -webkit-user-select: none;
        } 
        body{
            background-color: black;
        }
        #main{
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%,-50%); 
        }

        p{
            line-height: .001;
            font-weight: bold;
            color: white;
        }
        
    </style>
    <script>
        setInterval(()=>{
            const timestampInSeconds = Math.floor(new Date().getTime() / 1000);
            const age = timestampInSeconds - 1185351600
            document.getElementById("age").innerHTML = (age/3600/24/360).toFixed(7)
        },100)
        
    </script>
</head>
<body>
    <div id="main">
        <p style="font-family: 'Rubik Mono One';font-size: 40px">Age</p>
        <p id="age" style="font-family: 'Lilita One';font-size: 60px;"></p>
    </div>
</body>
</html>