auto_gray.html

<style>
    body.grayDay { 
        filter: progid:DXImageTransform.Microsoft.BasicImage(grayscale=1); 
        -webkit-filter: grayscale(100%); }
</style>
<script>
    window.onload = function() {
    var grayDay = [108, 207, 219, 404, 420, 512, 815, 909, 918, 1213];
    var today = new Date();
    var d = (today.getMonth() + 1) * 100 + today.getDate();
    grayDay.forEach(function(i) {
      if (i == d) {
        var classVal = document.getElementsByTagName('body')[0].getAttribute("class");
        classVal = classVal.concat(" grayDay");
        document.getElementsByTagName('body')[0].setAttribute("class", classVal);
      }
    });
  }
</script>