Add at the beginning of the page:
<script>
var now1 =new Date()
StarTime_S=now1.getTime()
</script>
Add before the end of the page:
Client: <script>
var now1 =new Date()
EndTime_S=now1.getTime()
document.write ((EndTime_S-StarTime_S)+"ms");
</script>
That’s it.