* cookies are on the fast path.
 */
private val STANDARD_DATE_FORMAT =
  object : ThreadLocal<DateFormat>() {
    override fun initialValue(): DateFormat {
      // Date format specified by RFC 7231 section 7.1.1.1.
      return SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss 'GMT'", Locale.US).apply {
        isLenient = false
        timeZone = UTC
      }
    }
  }