Hi, I have a problem with my biography

Hello, I also have a problem, when I add a script in Java that is <script>. </scripts> my biography is automatically deleted, do you have any idea why? Specifically, I’m trying to put this script in

<script language="javascript">
<!-- hide from old browsers
var today = new Date()
var targetDate = new Date("026/24/2018") //Opening date site
var timeAfterTarget = Math.floor(( today.getTime() - targetDate.getTime() ) / 86400000)
var msg = "BDT currentlyasdasdas has <b>" + timeAfterTarget + " </b> days"
document.write(msg)
//-->
</script>

After clicking on the update button, this code disappears and I don’t understand why, maybe someone knows why it is deleted, I’m waiting for a nice answer and I hope I made myself understood, I’m from Romania!