function check_transport_time($deptime, $rettime){
  include_once 'functions.php';
  sethin();

  $deptimeXS = strtotime($deptime);
  $rettimeXS = strtotime($rettime);
  
  $duration = $rettimeXS - $deptimeXS;
  
  $dur =  210 * 60 ; // making 3 1/2 hours as seconds
  
  if  ($duration > $dur) {
    include_once 'menu_html.php';
    display_confirmation ("Error", "The return time is more than 3 <sup>1/2</sup> Hours from Departure Time. Please go <A HREF="javascript:history.go(-1)">back</a> to fix this");
  }
}