diff --git a/pkg/machinepolicies/duration_formatter_test.go b/pkg/machinepolicies/duration_formatter_test.go
index ee863026..e3946591 100644
--- a/pkg/machinepolicies/duration_formatter_test.go
+++ b/pkg/machinepolicies/duration_formatter_test.go
@@ -12,6 +12,8 @@ func TestFromTimeSpanParsesDayComponent(t *testing.T) {
 	assert.Equal(t, 24*time.Hour, FromTimeSpan("01.00:00:00"))
 	assert.Equal(t, 48*time.Hour, FromTimeSpan("2.00:00:00"))
 	assert.Equal(t, 25*time.Hour+30*time.Minute, FromTimeSpan("1.01:30:00"))
+	// The server does not pad the day component, so it can be arbitrarily wide.
+	assert.Equal(t, 900000*time.Hour, FromTimeSpan("37500.00:00:00"))
 }
 
 func TestFromTimeSpanParsesTimeOnly(t *testing.T) {
@@ -26,11 +28,15 @@ func TestFromTimeSpanParsesFractionalSeconds(t *testing.T) {
 	// ToTimeSpan emits a 5-digit fraction rather than .NET's 7, so it must round-trip too.
 	assert.Equal(t, 500*time.Millisecond, FromTimeSpan("00:00:00.50000"))
 	assert.Equal(t, time.Second+500*time.Millisecond, FromTimeSpan("1.00:00:01.50000")-24*time.Hour)
+	assert.Equal(t, 24*time.Hour+500*time.Millisecond, FromTimeSpan("01.00:00:00.50000"))
 }
 
 func TestFromTimeSpanHandlesEmptyAndMalformed(t *testing.T) {
 	assert.Equal(t, time.Duration(0), FromTimeSpan(""))
 	assert.Equal(t, time.Duration(0), FromTimeSpan("not-a-timespan"))
+	// Too few and too many colon-separated fields.
+	assert.Equal(t, time.Duration(0), FromTimeSpan("00:00"))
+	assert.Equal(t, time.Duration(0), FromTimeSpan("00:00:00:00"))
 }
 
 func TestFromTimeSpanHandlesNegative(t *testing.T) {
@@ -38,6 +44,26 @@ func TestFromTimeSpanHandlesNegative(t *testing.T) {
 	assert.Equal(t, -25*time.Hour, FromTimeSpan("-1.01:00:00"))
 }
 
+func TestToTimeSpanRendersDotNetFormat(t *testing.T) {
+	// The day and fractional-second components are only rendered when non-zero, and the
+	// round-trip test cannot tell a formatting change from a matching parsing change.
+	for _, c := range []struct {
+		duration time.Duration
+		expected string
+	}{
+		{500 * time.Millisecond, "00:00:00.50000"},
+		{1111 * time.Millisecond, "00:00:01.11100"},
+		{time.Second, "00:00:01"},
+		{time.Minute, "00:01:00"},
+		{time.Hour, "01:00:00"},
+		{2 * time.Hour, "02:00:00"},
+		{47 * time.Hour, "01.23:00:00"},
+		{48 * time.Hour, "02.00:00:00"},
+	} {
+		assert.Equal(t, c.expected, ToTimeSpan(c.duration), "ToTimeSpan(%s)", c.duration)
+	}
+}
+
 func TestToTimeSpanFromTimeSpanRoundTrip(t *testing.T) {
 	for _, d := range []time.Duration{
 		0,
diff --git a/pkg/machines/duration_formatter_test.go b/pkg/machines/duration_formatter_test.go
index 42fe00ac..48fd6569 100644
--- a/pkg/machines/duration_formatter_test.go
+++ b/pkg/machines/duration_formatter_test.go
@@ -12,6 +12,8 @@ func TestFromTimeSpanParsesDayComponent(t *testing.T) {
 	assert.Equal(t, 24*time.Hour, FromTimeSpan("01.00:00:00"))
 	assert.Equal(t, 48*time.Hour, FromTimeSpan("2.00:00:00"))
 	assert.Equal(t, 25*time.Hour+30*time.Minute, FromTimeSpan("1.01:30:00"))
+	// The server does not pad the day component, so it can be arbitrarily wide.
+	assert.Equal(t, 900000*time.Hour, FromTimeSpan("37500.00:00:00"))
 }
 
 func TestFromTimeSpanParsesTimeOnly(t *testing.T) {
@@ -26,11 +28,15 @@ func TestFromTimeSpanParsesFractionalSeconds(t *testing.T) {
 	// ToTimeSpan emits a 5-digit fraction rather than .NET's 7, so it must round-trip too.
 	assert.Equal(t, 500*time.Millisecond, FromTimeSpan("00:00:00.50000"))
 	assert.Equal(t, time.Second+500*time.Millisecond, FromTimeSpan("1.00:00:01.50000")-24*time.Hour)
+	assert.Equal(t, 24*time.Hour+500*time.Millisecond, FromTimeSpan("01.00:00:00.50000"))
 }
 
 func TestFromTimeSpanHandlesEmptyAndMalformed(t *testing.T) {
 	assert.Equal(t, time.Duration(0), FromTimeSpan(""))
 	assert.Equal(t, time.Duration(0), FromTimeSpan("not-a-timespan"))
+	// Too few and too many colon-separated fields.
+	assert.Equal(t, time.Duration(0), FromTimeSpan("00:00"))
+	assert.Equal(t, time.Duration(0), FromTimeSpan("00:00:00:00"))
 }
 
 func TestFromTimeSpanHandlesNegative(t *testing.T) {
@@ -38,6 +44,26 @@ func TestFromTimeSpanHandlesNegative(t *testing.T) {
 	assert.Equal(t, -25*time.Hour, FromTimeSpan("-1.01:00:00"))
 }
 
+func TestToTimeSpanRendersDotNetFormat(t *testing.T) {
+	// The day and fractional-second components are only rendered when non-zero, and the
+	// round-trip test cannot tell a formatting change from a matching parsing change.
+	for _, c := range []struct {
+		duration time.Duration
+		expected string
+	}{
+		{500 * time.Millisecond, "00:00:00.50000"},
+		{1111 * time.Millisecond, "00:00:01.11100"},
+		{time.Second, "00:00:01"},
+		{time.Minute, "00:01:00"},
+		{time.Hour, "01:00:00"},
+		{2 * time.Hour, "02:00:00"},
+		{47 * time.Hour, "01.23:00:00"},
+		{48 * time.Hour, "02.00:00:00"},
+	} {
+		assert.Equal(t, c.expected, ToTimeSpan(c.duration), "ToTimeSpan(%s)", c.duration)
+	}
+}
+
 func TestToTimeSpanFromTimeSpanRoundTrip(t *testing.T) {
 	for _, d := range []time.Duration{
 		0,