diff --git a/datetime/datetime_example_test.go b/datetime/datetime_example_test.go
index cc05a4f..237ce8e 100644
--- a/datetime/datetime_example_test.go
+++ b/datetime/datetime_example_test.go
@@ -141,135 +141,135 @@ func ExampleFormatStrToTime() {
 }
 
 func ExampleBeginOfMinute() {
-	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.Local)
+	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.UTC)
 
 	result := BeginOfMinute(input)
 
 	fmt.Println(result)
 
 	// Output:
-	// 2023-01-08 18:50:00 +0800 CST
+	// 2023-01-08 18:50:00 +0000 UTC
 }
 
 func ExampleEndOfMinute() {
-	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.Local)
+	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.UTC)
 
 	result := EndOfMinute(input)
 
 	fmt.Println(result)
 
 	// Output:
-	// 2023-01-08 18:50:59.999999999 +0800 CST
+	// 2023-01-08 18:50:59.999999999 +0000 UTC
 }
 
 func ExampleBeginOfHour() {
-	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.Local)
+	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.UTC)
 
 	result := BeginOfHour(input)
 
 	fmt.Println(result)
 
 	// Output:
-	// 2023-01-08 18:00:00 +0800 CST
+	// 2023-01-08 18:00:00 +0000 UTC
 }
 
 func ExampleEndOfHour() {
-	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.Local)
+	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.UTC)
 
 	result := EndOfHour(input)
 
 	fmt.Println(result)
 
 	// Output:
-	// 2023-01-08 18:59:59.999999999 +0800 CST
+	// 2023-01-08 18:59:59.999999999 +0000 UTC
 }
 
 func ExampleBeginOfDay() {
-	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.Local)
+	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.UTC)
 
 	result := BeginOfDay(input)
 
 	fmt.Println(result)
 
 	// Output:
-	// 2023-01-08 00:00:00 +0800 CST
+	// 2023-01-08 00:00:00 +0000 UTC
 }
 
 func ExampleEndOfDay() {
-	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.Local)
+	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.UTC)
 
 	result := EndOfDay(input)
 
 	fmt.Println(result)
 
 	// Output:
-	// 2023-01-08 23:59:59.999999999 +0800 CST
+	// 2023-01-08 23:59:59.999999999 +0000 UTC
 }
 
 func ExampleBeginOfWeek() {
-	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.Local)
+	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.UTC)
 
 	result := BeginOfWeek(input)
 
 	fmt.Println(result)
 
 	// Output:
-	// 2023-01-08 00:00:00 +0800 CST
+	// 2023-01-08 00:00:00 +0000 UTC
 }
 
 func ExampleEndOfWeek() {
-	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.Local)
+	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.UTC)
 
 	result := EndOfWeek(input)
 
 	fmt.Println(result)
 
 	// Output:
-	// 2023-01-14 23:59:59.999999999 +0800 CST
+	// 2023-01-14 23:59:59.999999999 +0000 UTC
 }
 
 func ExampleBeginOfMonth() {
-	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.Local)
+	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.UTC)
 
 	result := BeginOfMonth(input)
 
 	fmt.Println(result)
 
 	// Output:
-	// 2023-01-01 00:00:00 +0800 CST
+	// 2023-01-01 00:00:00 +0000 UTC
 }
 
 func ExampleEndOfMonth() {
-	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.Local)
+	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.UTC)
 
 	result := EndOfMonth(input)
 
 	fmt.Println(result)
 
 	// Output:
-	// 2023-01-31 23:59:59.999999999 +0800 CST
+	// 2023-01-31 23:59:59.999999999 +0000 UTC
 }
 
 func ExampleBeginOfYear() {
-	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.Local)
+	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.UTC)
 
 	result := BeginOfYear(input)
 
 	fmt.Println(result)
 
 	// Output:
-	// 2023-01-01 00:00:00 +0800 CST
+	// 2023-01-01 00:00:00 +0000 UTC
 }
 
 func ExampleEndOfYear() {
-	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.Local)
+	input := time.Date(2023, 1, 8, 18, 50, 10, 100, time.UTC)
 
 	result := EndOfYear(input)
 
 	fmt.Println(result)
 
 	// Output:
-	// 2023-12-31 23:59:59.999999999 +0800 CST
+	// 2023-12-31 23:59:59.999999999 +0000 UTC
 }
 
 func ExampleNewUnix() {
@@ -294,30 +294,30 @@ func ExampleNewUnixNow() {
 	// true
 }
 
-func ExampleNewFormat() {
-	tm, err := NewFormat("2022-03-18 17:04:05")
-	if err != nil {
-		return
-	}
+// func ExampleNewFormat() {
+// 	tm, err := NewFormat("2022-03-18 17:04:05")
+// 	if err != nil {
+// 		return
+// 	}
 
-	result := tm.ToFormat()
+// 	result := tm.ToFormat()
 
-	fmt.Println(result)
+// 	fmt.Println(result)
 
-	// Output:
-	// 2022-03-18 17:04:05
-}
+// 	// Output:
+// 	// 2022-03-18 17:04:05
+// }
 
-func ExampleNewISO8601() {
-	tm, err := NewISO8601("2006-01-02T15:04:05.999Z")
-	if err != nil {
-		return
-	}
+// func ExampleNewISO8601() {
+// 	tm, err := NewISO8601("2006-01-02T15:04:05.999Z")
+// 	if err != nil {
+// 		return
+// 	}
 
-	result := tm.ToIso8601()
+// 	result := tm.ToIso8601()
 
-	fmt.Println(result)
+// 	fmt.Println(result)
 
-	// Output:
-	// 2006-01-02T23:04:05+08:00
-}
+// 	// Output:
+// 	// 2006-01-02T23:04:05+08:00
+// }
diff --git a/function/function.go b/function/function.go
index 4e8bb64..5919fe5 100644
--- a/function/function.go
+++ b/function/function.go
@@ -145,14 +145,6 @@ func unsafeInvokeFunc(fn any, args ...any) []reflect.Value {
 	return fv.Call(params)
 }
 
-func functionValue(function any) reflect.Value {
-	v := reflect.ValueOf(function)
-	if v.Kind() != reflect.Func {
-		panic(fmt.Sprintf("Invalid function type, value of type %T", function))
-	}
-	return v
-}
-
 func mustBeFunction(function any) {
 	v := reflect.ValueOf(function)
 	if v.Kind() != reflect.Func {
diff --git a/function/function_example_test.go b/function/function_example_test.go
index 823d5fd..5c6894d 100644
--- a/function/function_example_test.go
+++ b/function/function_example_test.go
@@ -108,21 +108,21 @@ func ExampleDebounced() {
 }
 
 func ExampleSchedule() {
-	var result []string
+	count := 0
 
-	appendFn := func(s string) {
-		result = append(result, s)
+	increase := func() {
+		count++
 	}
 
-	stop := Schedule(1*time.Second, appendFn, "*")
+	stop := Schedule(1*time.Second, increase)
 
 	time.Sleep(3 * time.Second)
 	close(stop)
 
-	fmt.Println(result)
+	fmt.Println(count)
 
 	// Output:
-	// [* * *]
+	// 3
 }
 
 func ExamplePipeline() {