val delta = servedMillis - lastModified!!.time
        return if (delta > 0L) delta / 10 else 0L
      }

      return 0L
    }

    /**
     * Returns the current age of the response, in milliseconds. The calculation is specified by RFC
     * 7234, 4.2.3 Calculating Age.
     */
    private fun cacheResponseAge(): Long {
      val servedDate = this.servedDate