Another solution would be to only replace it in the validation...
so on the insert page line 25 you can change it to:
$WAFV_Errors .= WAValidateDT(((isset($_POST["dob"]))?str_replace("-","/",$_POST["dob"]):"") . "",true,"\b(1[0-2]|0[1-9])/([12]\d|3[0-1]|0[1-9])/\d{4}\b","","",false,".*","","",true,13);