document.getElementById('txtboxId').select()
if(preg_match('/^(0?[1-9]|1[0-2])\/(0?[1-9]|[12][0-9]|3[01])\/((19|20)\d{2})$/', $_POST['start_date']) == 0) echo 'The given date is not in the format(mm/dd/yyyy)
UNIX_TIMESTAMP(STR_TO_DATE( 'mm/dd/yyyy', '%m/%d/%Y' ))