<html>
<head>
<title>Страница</title>
</head>
<body>
<a href=index.htm><img id='pd'></a>
<script>
const picurls = [
'/images/1.jpg',
'/images/2.jpg',
'/images/3.jpg',
];
const now = Date.now(); // мс с 01.01.1970
const msinday = 1000*60*60*24; // мс в сутках
const nowDay = Math.trunc(now/msinday); // дней с 01.01.1970
const ind = nowDay % picurls.length;
const url = picurls[ind];
document.getElementById('pd').src = url
</script>
</body>
</html>