Please attach the page you are working on so I can take a look. The issue has to be in the value you have set for the input field:
<?php echo(isset($_GET['v1'])?ValidatedField("healthscreeningform_984","DOB"):$rsEDITFORM->getColumnVal("SMCformDOB")?date("d-m-Y",strtotime($rsEDITFORM->getColumnVal("SMCformDOB"))):"") ?>
this code looks like it is set to use the server validation value when $_GET['v1'] is set. So the issue may be that the server validation doesn't set that get variable. Another possibility is that the validated field reference is wrong.
I'll go to the other post to take a look. In the future please don't post the same issue multiple times. It is too confusing to keep track of if and when I've answered it and what information I do or don't have.