if zoneName != "" {
		t := Date(year, Month(month), day, hour, min, sec, nsec, UTC)
		// Look for local zone with the given offset.
		// If that zone was in effect at the given time, use it.
		offset, ok := local.lookupName(zoneName, t.unixSec())
		if ok {
			t.addSec(-int64(offset))
			t.setLoc(local)
			return t, nil
		}

		// Otherwise, create fake zone with unknown offset.

			f: func(t *testing.T) {
				expectedErr := &DNSError{Err: errMalformedDNSRecordsDetail, Name: "golang.org"}
				_, err := r.LookupCNAME(context.Background(), "golang.org")
				if err.Error() != expectedErr.Error() {
					t.Fatalf("unexpected error: %s", err)
				}
				_, err = LookupCNAME("golang.org")
				if err.Error() != expectedErr.Error() {
					t.Fatalf("unexpected error: %s", err)
				}
			},
		},