monthly recur fix

internal/task/recur.go

@@ -260,7 +260,18 @@ func (enm EveryNMonths) RecursOn(date Date) bool {
 		return false
 	}
 
-	return enm.Start.Day() == date.Day()
+	tDate := enm.Start
+	for {
+		if tDate.Equal(date) {
+			return true
+		}
+		if tDate.After(date) {
+			return false
+		}
+		tYear, tMonth, tDay := tDate.Time().Date()
+		tDate = NewDate(tYear, int(tMonth)+enm.N, tDay)
+	}
+
 }
 
 func (enm EveryNMonths) String() string {

internal/task/recur_test.go

@@ -338,6 +338,19 @@ func TestEveryNMonths(t *testing.T) {
 			{
 				name: "one month",
 				date: task.NewDate(2021, 3, 3),
+			},
+			{
+				name: "3 months",
+				date: task.NewDate(2021, 5, 3),
+				exp:  true,
+			},
+			{
+				name: "4 months",
+				date: task.NewDate(2021, 6, 3),
+			},
+			{
+				name: "6 months",
+				date: task.NewDate(2021, 8, 3),
 				exp:  true,
 			},
 		} {