Untitled

<head>
  <script src="https://code.jquery.com/jquery-1.12.4.js"></script>
  <script src="https://code.jquery.com/ui/1.12.1/jquery-ui.js"></script>
  <link rel="stylesheet" href="https://code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css"/>
  <script>
  $( function() {
    $( "#datepicker" ).datepicker();
  } );
</script>
</head>


<input id="inaltime"></a>
<input type="button" onclick="check()" value="click" />
<p>Date: <input type="text" id="datepicker"></p>
<script>
    function check() {
        if (isNaN(document.getElementById("inaltime").value))
            console.log("introdu inatlime");
        else
            console.log("BAAA E BINE");
    }

</script>