Last 30 days of astronomy pic of the day.

<html>
<head>
  <style>
  .gallery {
    clear: both;
  }
  .apod_img_class {
    width: 23%;
    margin: 1%;
    float: left;
  }
  body {
    margin: auto;
    max-width: 95%;
  }
  iframe {
    border: none;
  }
  </style>
</head>
<body>
  <div class="gallery">

</div>

var today = new Date();

//for loop to go back a day for a set number of days
  for (var dayBack = 0; dayBack < 30; dayBack++) {
    var requestDate = new Date();
    requestDate.setDate(today.getDate() - dayBack);
    var queryString = requestDate.getFullYear()+"-"+parseInt(requestDate.getMonth()+1)+"-"+requestDate.getDate()
    getImage(queryString);
  }

function getImage(date) {

var url = "https://api.nasa.gov/planetary/apod?concept_tags=True&date="+ date +"&hd=True&api_key=NNKOjkoul8n1CH18TWA9gwngW1s1SmjESPjNoUFo";

$.ajax({
      url: url,
      success: handleResult
    });
    function handleResult(result){
      if(result.media_type != "video") {
        $( ".gallery" ).append( "<img class='apod_img_class' src='"+ result.url +"' alt='"+ result.explanation +"'>" );
      }
    }

}

</script>

https://code.jquery.com/jquery-2.1.4.min.js