Add a simple one-hour offset to the times included in the iCal data, if a custom field value is present. Useful for sites that have events in different timezones

ical_offset_example.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

add_filter(
  'FHEE__EED_Ical__download_ics_file_ics_data',
  'my_custom_ical_timezone_output_filter',
  10,
  2
);

function my_custom_ical_timezone_output_filter(
  $ics_data, 
  $datetime
) {
  $event = $datetime->event();
  if($event instanceof EE_Event) {
    $tz = $event->get_post_meta('event_timezone', true);
    if(isset($tz) && $tz == 'Pacific') {
      $ics_data['DTSTART'] = date(
        EED_Ical::iCal_datetime_format, 
        $datetime->start() + HOUR_IN_SECONDS
      );
      $ics_data['DTEND'] = date(
        EED_Ical::iCal_datetime_format, 
        $datetime->end() + HOUR_IN_SECONDS
      );
    }
  }
  return $ics_data;
}