TimezoneController.php

<?php

namespace Drupal\system\Controller;

use Symfony\Component\HttpFoundation\JsonResponse;

/**
 * Provides a callback for finding out a timezone name.
 */
class TimezoneController {
    
    /**
     * Retrieve a JSON object containing a time zone name given a timezone
     * abbreviation.
     *
     * @param string $abbreviation
     *   Time zone abbreviation.
     * @param int $offset
     *   Offset from GMT in seconds. Defaults to -1 which means that first found
     *   time zone corresponding to abbr is returned. Otherwise exact offset is
     *   searched and only if not found then the first time zone with any offset
     *   is returned.
     * @param null|bool $is_daylight_saving_time
     *   Daylight saving time indicator. If abbr does not exist then the time
     *   zone is searched solely by offset and isdst.
     *
     * @return \Symfony\Component\HttpFoundation\JsonResponse
     *   The timezone name in JsonResponse object.
     */
    public function getTimezone($abbreviation = '', $offset = -1, $is_daylight_saving_time = NULL) {
        // An abbreviation of "0" passed in the callback arguments should be
        // interpreted as the empty string.
        $abbreviation = $abbreviation ? $abbreviation : '';
        $timezone = timezone_name_from_abbr($abbreviation, intval($offset), $is_daylight_saving_time);
        return new JsonResponse($timezone);
    }

}