Method date

/**
 * Returns formatted date according to a given format and time zone.
 *
 * @param   string   $input      String in a format accepted by date(), defaults to "now".
 * @param   string   $format     The date format specification string (see {@link PHP_MANUAL#date}).
 * @param   mixed    $tz         Time zone to be used for the date.  Special cases: boolean true for user
 *                               setting, boolean false for server setting.
 * @param   boolean  $gregorian  True to use Gregorian calendar.
 *
 * @return  string    A date translated by the given format and time zone.
 *
 * @see     strftime
 * @since   1.5
 */
public static function date($input = 'now', $format = null, $tz = true, $gregorian = false)
{
    $app = Factory::getApplication();
    // UTC date converted to user time zone.
    if ($tz === true) {
        // Get a date object based on UTC.
        $date = Factory::getDate($input, 'UTC');
        // Set the correct time zone based on the user configuration.
        $date->setTimezone($app->getIdentity()->getTimezone());
    } elseif ($tz === false) {
        // Get a date object based on UTC.
        $date = Factory::getDate($input, 'UTC');
        // Set the correct time zone based on the server configuration.
        $date->setTimezone(new \DateTimeZone($app->get('offset')));
    } elseif ($tz === null) {
        $date = Factory::getDate($input);
    } else {
        // Get a date object based on UTC.
        $date = Factory::getDate($input, 'UTC');
        // Set the correct time zone based on the server configuration.
        $date->setTimezone(new \DateTimeZone($tz));
    }
    // If no format is given use the default locale based format.
    if (!$format) {
        $format = Text::_('DATE_FORMAT_LC1');
    } elseif (Factory::getLanguage()->hasKey($format)) {
        $format = Text::_($format);
    }
    if ($gregorian) {
        return $date->format($format, true);
    }
    return $date->calendar($format, true);
}