JS calculation time difference

    <script type="text/javascript">         
        var date1= '2015/05/01 00:00:00'; //start time 
        var date2 = new Date(); //end time 
        var date3 = date2.getTime() - new Date(date1).getTime(); //Time difference in milliseconds       
     
        //-------------------------------------------- 
     
        / /Calculate the difference in days 
        var days=Math.floor(date3/(24*3600*1000)) 
     
        //Calculate the number of hours 
     
        var leave1=date3%(24*3600*1000) //The number of milliseconds remaining after calculating the number of days 
        var hours=Math.floor(leave1/(3600*1000)) 
        //Calculate the difference in minutes 
        var leave2=leave1%(3600*1000) //The number of milliseconds remaining after calculating the hours 
        var minutes=Math.floor(leave2/( 60*1000)) 
        //Calculate the difference in seconds 
        var leave3=leave2%(60*1000) //The number of milliseconds remaining after calculating the number of minutes 
        var seconds=Math.round(leave3/1000) 
        alert("Difference"+days+"days"+hours+"hours"+minutes+" minutes "+seconds+" seconds") 
    </script>