= Workaround =====
<html>
<script>
function date_as_slug( date )
{
var y = date.getFullYear(),
m = ... n<10?'0'+mn:mn) ;
}
document.write( '<b>' + date_as_slug(new Date()) +'</b><br/>' );
var date = '04/... ument.write('<b>' + date +' => '+ d +' => '+ date_as_slug( d ) +'</b><br/>');
date = '2018-05-04';
d ... ument.write('<b>' + date +' => '+ d +' => '+ date_as_slug( d ) +'</b><br/>');
</script>
</html>
====
