ExpressiveDate::addOneDay PHP Method

    public function addOneDay()
    {
        return $this->modifyDays(1);
    }

function eme_ical_single_event($event, $title_format, $description_format) {
   global $eme_timezone;
   $title = eme_sanitize_ical (eme_replace_placeholders ( $title_format, $event, "text" ));
   $description = eme_sanitize_ical (eme_replace_placeholders ( $description_format, $event, "text" ));
   $html_description = eme_sanitize_ical (eme_replace_placeholders ( $description_format, $event, "html" ),1);

   $event_link = eme_event_url($event);
   $startstring=new ExpressiveDate($event['event_start_date']." ".$event['event_start_time'],$eme_timezone);
   $dtstartdate=$startstring->format("Ymd");
   $dtstarthour=$startstring->format("His");
   //$dtstart=$dtstartdate."T".$dtstarthour."Z";
   // we'll use localtime, so no "Z"
   $dtstart=$dtstartdate."T".$dtstarthour;
   if ($event['event_end_date'] == "")
      $event['event_end_date'] = $event['event_start_date'];
   if ($event['event_end_time'] == "")
      $event['event_end_time'] = $event['event_start_time'];
   $endstring=$event['event_end_date']." ".$event['event_end_time'];
   $endstring=new ExpressiveDate($event['event_end_date']." ".$event['event_end_time'],$eme_timezone);
   $dtenddate=$endstring->format("Ymd");
   $dtendhour=$endstring->format("His");
   //$dtend=$dtenddate."T".$dtendhour."Z";
   // we'll use localtime, so no "Z"
   $dtend=$dtenddate."T".$dtendhour;
   $tzstring = get_option('timezone_string');

   $res = "";
   $res .= "BEGIN:VEVENT\r\n";
   //DTSTAMP must be in UTC format, so adding "Z" as well
   $res .= "DTSTAMP:" . gmdate('Ymd').'T'. gmdate('His') . "Z\r\n";
   if ($event['event_properties']['all_day']) {
      // ical standard for an all day event: specify only the day, meaning
      // an 'all day' event is flagged as starting at the beginning of one day and lasting until the beginning of the next
      // so it is the same as adding "T000000" as time spec to the start/end datestring
      // But since it "ends" at the beginning of the next day, we should add 24 hours, otherwise the event ends one day too soon
      $dtenddate=$endstring->addOneDay()->format('Ymd');
      $res .= "DTSTART;VALUE=DATE:$dtstartdate\r\n";
      $res .= "DTEND;VALUE=DATE:$dtenddate\r\n";
   } else {
      $res .= "DTSTART;TZID=$tzstring:$dtstart\r\n";
      $res .= "DTEND;TZID=$tzstring:$dtend\r\n";
   }
   $res .= "UID:$dtstart-$dtend-".$event['event_id']."@".$_SERVER['SERVER_NAME']."\r\n";
   $res .= "SUMMARY:$title\r\n";
   $res .= "DESCRIPTION:$description\r\n";
   $res .= "X-ALT-DESC;FMTTYPE=text/html:$html_description\r\n";
   $res .= "URL:$event_link\r\n";
   $res .= "ATTACH:$event_link\r\n";
   if ($event['event_image_id']) {
      $thumb_array = image_downsize( $event['event_image_id'], get_option('eme_thumbnail_size') );
      $thumb_url = $thumb_array[0];
      $res .= "ATTACH:$thumb_url\r\n";
   }
   if (isset($event['location_id']) && $event['location_id']) {
      $location = eme_sanitize_ical (eme_replace_placeholders ( "#_LOCATION, #_ADDRESS, #_TOWN", $event, "text" ));
      $res .= "LOCATION:$location\r\n";
   }
   $res .= "END:VEVENT\r\n";
   return $res;
}