doc: add doc for DayOfYear

datetime/datetime.go

@@ -238,9 +238,12 @@ func BetweenSeconds(t1 time.Time, t2 time.Time) int64 {
 	return index
 }
 
-func DayOfYear(t1 time.Time) int {
-	y, m, d := t1.Date()
-	firstDay := time.Date(y, 1, 1, 0, 0, 0, 0, t1.Location())
-	nowDate := time.Date(y, m, d, 0, 0, 0, 0, t1.Location())
+// DayOfYear returns which day of the year the parameter date `t` is.
+// Play: todo
+func DayOfYear(t time.Time) int {
+	y, m, d := t.Date()
+	firstDay := time.Date(y, 1, 1, 0, 0, 0, 0, t.Location())
+	nowDate := time.Date(y, m, d, 0, 0, 0, 0, t.Location())
+
 	return int(nowDate.Sub(firstDay).Hours() / 24)
 }

datetime/datetime_example_test.go

@@ -369,3 +369,23 @@ func ExampleBetweenSeconds() {
 	// 86400
 	// -86400
 }
+
+func ExampleDayOfYear() {
+	date1 := time.Date(2023, 02, 01, 1, 1, 1, 0, time.Local)
+	result1 := DayOfYear(date1)
+
+	date2 := time.Date(2023, 01, 02, 1, 1, 1, 0, time.Local)
+	result2 := DayOfYear(date2)
+
+	date3 := time.Date(2023, 01, 01, 1, 1, 1, 0, time.Local)
+	result3 := DayOfYear(date3)
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+	fmt.Println(result3)
+
+	// Output:
+	// 31
+	// 1
+	// 0
+}

datetime/datetime_test.go

@@ -274,15 +274,15 @@ func TestIsLeapYear(t *testing.T) {
 
 func TestDayOfYear(t *testing.T) {
 	assert := internal.NewAssert(t, "TestDayOfYear")
-	date := time.Date(2023, 02, 01, 1, 1, 1, 0, time.Local)
-	result := DayOfYear(date)
-	assert.Equal(31, result)
-
-	date1 := time.Date(2023, 01, 02, 1, 1, 1, 0, time.Local)
+	date1 := time.Date(2023, 02, 01, 1, 1, 1, 0, time.Local)
 	result1 := DayOfYear(date1)
-	assert.Equal(1, result1)
+	assert.Equal(31, result1)
+
+	date2 := time.Date(2023, 01, 02, 1, 1, 1, 0, time.Local)
+	result2 := DayOfYear(date2)
+	assert.Equal(1, result2)
 
 	date3 := time.Date(2023, 01, 01, 1, 1, 1, 0, time.Local)
-	result2 := DayOfYear(date3)
-	assert.Equal(0, result2)
+	result3 := DayOfYear(date3)
+	assert.Equal(0, result3)
 }