nextcloud-server/apps/calendar/ajax/timezonedetection.php

<?php
/**
 * Copyright (c) 2011, 2012 Georg Ehrke <ownclouddev at georgswebsite dot de>
 * This file is licensed under the Affero General Public License version 3 or
 * later.
 * See the COPYING-README file.
 */
require_once ("../../../lib/base.php");
OC_JSON::checkLoggedIn();
OC_JSON::checkAppEnabled('calendar');
if($_POST['timezonedetection'] == 'on'){
	OC_Preferences::setValue(OC_USER::getUser(), 'calendar', 'timezonedetection', 'true');
}else{
	OC_Preferences::setValue(OC_USER::getUser(), 'calendar', 'timezonedetection', 'false');
}
OC_JSON::success();