TimeZone.php

<?php

namespace Drupal\system\Plugin\migrate\process\d6;

use Drupal\migrate\Attribute\MigrateProcess;
use Drupal\migrate\MigrateExecutableInterface;
use Drupal\migrate\ProcessPluginBase;
use Drupal\migrate\Row;

/**
 * Process the D6 Timezone offset into a D8 compatible timezone name.
 */
class TimeZone extends ProcessPluginBase {
    
    /**
     * {@inheritdoc}
     */
    public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
        $offset = $value;
        // Convert the integer value of the offset (which can be either
        // negative or positive) to a timezone name.
        // Note: Daylight saving time is not to be used.
        $timezone_name = timezone_name_from_abbr('', intval($offset), 0);
        if (!$timezone_name) {
            $timezone_name = 'UTC';
        }
        return $timezone_name;
    }

}