public function defaultValue()
    {
        if ($this->default === null) {
            return null;
        }

        $default = $this->default;

        if (strstr($this->default, '{{') && strstr($this->default, '}}')) {
            // Parse special replacements (if we have one)
            $default = str_replace("{{CURRENT_TIME}}", date('c', time()), $default);
        }

        return $default;
    }