var duration time.Duration
	switch timePart {
	case timePartYear:
		return FromTimestamp(t.AddDate(int(qty), 0, 0)), nil
	case timePartMonth:
		return FromTimestamp(t.AddDate(0, int(qty), 0)), nil
	case timePartDay:
		return FromTimestamp(t.AddDate(0, 0, int(qty))), nil
	case timePartHour:
		duration = time.Duration(qty) * time.Hour
	case timePartMinute:

		formValues.Set("X-Amz-Algorithm", tt.XAmzAlgorithm)
		formValues.Set("X-Amz-Credential", tt.XAmzCredential)
		if tt.Expired {
			// Expired already.
			pp.SetExpires(UTCNow().AddDate(0, 0, -10))
		} else {
			// Expires in 10 days.
			pp.SetExpires(UTCNow().AddDate(0, 0, 10))
		}

		formValues.Set("Policy", base64.StdEncoding.EncodeToString([]byte(pp.String())))
		formValues.Set("Success_action_status", tt.SuccessActionStatus)

    ).isEqualTo(10L)
    assertThat(
      Headers.Builder()
        .add("abc", "def")
        .add("ghi", "jkl")
        .build()
        .byteCount(),
    ).isEqualTo(20L)
  }

  @Test fun addDate() {
    val expected = Date(0L)
    val headers =
      Headers.Builder()
        .add("testDate", expected)
        .build()
    assertThat(headers["testDate"]).isEqualTo("Thu, 01 Jan 1970 00:00:00 GMT")