date and time zero value

item/date.go

@@ -167,7 +167,7 @@ func (d Date) DaysBetween(d2 Date) int {
 
 func (d Date) String() string {
 	if d.t.IsZero() {
-		return "no date"
+		return ""
 	}
 
 	return strings.ToLower(d.t.Format(DateFormat))

item/date_test.go

@@ -230,7 +230,7 @@ func TestDateString(t *testing.T) {
 		{
 			name: "zero",
 			date: item.NewDate(0, 0, 0),
-			exp:  "no date",
+			exp:  "",
 		},
 		{
 			name: "normal",

item/task_test.go

@@ -102,7 +102,7 @@ func TestTaskItem(t *testing.T) {
 			expItem: item.Item{
 				Kind:    item.KindTask,
 				Updated: time.Time{},
-				Body:    `{"duration":"0s","title":"","time":"00:00"}`,
+				Body:    `{"duration":"0s","title":"","time":""}`,
 			},
 		},
 		{

item/time.go

@@ -44,6 +44,10 @@ func NewTimeFromString(timeStr string) Time {
 }
 
 func (t *Time) String() string {
+	if t.t.IsZero() {
+		return ""
+	}
+
 	return t.t.Format(TimeFormat)
 }
 

item/time_test.go

@@ -44,11 +44,16 @@ func TestTimeFromString(t *testing.T) {
 	}{
 		{
 			name: "empty",
-			exp:  "00:00",
+			exp:  "",
 		},
 		{
 			name: "invalid",
 			str:  "invalid",
+			exp:  "",
+		},
+		{
+			name: "00:00",
+			str:  "00:00",
 			exp:  "00:00",
 		},
 		{