The Events Calendar - Event Aggregator: hijack event time zone before import

functions.php

<?php

/**
  * The Events Calendar - Event Aggregator: hijack event time zone before import
  * Must change code to accomodate your desired time zone
  * 
  * From https://gist.github.com/cliffordp/f2cf6b3ce9f33c7ff17988c824d67e21
  * 
  * By Nico 2017-01-12
  */
function tribe_ea_modify_timezone ( $event, $record ) {

	// if event has a timezone just return the event
	if ( $event['EventTimeZone'] ) return $event;

	// if it has no timezone let's convert the event to the site timezone
	$tz = new DateTimeZone('America/Denver');

	$start_date = new DateTime($event['EventStartDate'] . ' ' . $event['EventStartHour'] . ':' . $event['EventStartMinute'] . ':00', new DateTimeZone('UTC'));
	$start_date->setTimezone($tz);

	$event['EventStartDate']   = $start_date->format('Y-m-d');
	$event['EventStartHour']   = $start_date->format('H');
	$event['EventStartMinute'] = $start_date->format('i');

	$end_date = new DateTime($event['EventEndDate'] . ' ' . $event['EventEndHour'] . ':' . $event['EventEndMinute'] . ':00', new DateTimeZone('UTC'));
	$end_date->setTimezone($tz);

	$event['EventEndDate']   = $end_date->format('Y-m-d');
	$event['EventEndHour']   = $end_date->format('H');
	$event['EventEndMinute'] = $end_date->format('i');
	
	return $event;
}
add_filter( 'tribe_aggregator_before_save_event', 'tribe_ea_modify_timezone', 10, 2);