diff --git a/CHANGELOG.md b/CHANGELOG.md
index 842183b..f963e47 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,8 @@
 # Changelog
 
+## 0.6.3
+- Support `ScheduledTask` management. see: example/jobs.dart.
+
 ## 0.6.2
 
 - Added support for intervals like `1-12/2`. [#55](https://github.com/agilord/cron/pull/55) by [ysahn-aplayz](https://github.com/ysahn-aplayz)
diff --git a/example/jobs.dart b/example/jobs.dart
new file mode 100644
index 0000000..cec6cd6
--- /dev/null
+++ b/example/jobs.dart
@@ -0,0 +1,124 @@
+import 'dart:async';
+
+import 'package:cron/cron.dart';
+
+enum JobAction { run, pause, stop, delete }
+
+enum JobTime {
+  hourly(expr: '0 * * * *'),
+  daily(expr: '0 0 * * *'),
+  weekly(expr: '0 0 * * 0'),
+  monthly(expr: '0 0 1 * *'),
+  yearly(expr: '0 0 1 1 *'),
+  midday12t(expr: '0 12 * * *'),
+  midday13t(expr: '0 13 * * * '),
+  afternoon15t(expr: '0 15 * * * '),
+  afternoon16t(expr: '0 16 * * * '),
+  every1mins(expr: '*/1 * * * *'),
+  every2mins(expr: '*/2 * * * *'),
+  every3mins(expr: '*/3 * * * *'),
+  every5mins(expr: '*/5 * * * *'),
+  expression(expr: '0 * * * *'),
+  ;
+
+  final String expr;
+  const JobTime({
+    required this.expr,
+  });
+}
+
+class Job {
+  JobTime time;
+  JobAction action;
+  String name;
+  String id;
+
+  Job(
+      {required this.action,
+      required this.time,
+      required this.name,
+      required this.id});
+
+  void cancel() {
+    action = JobAction.stop;
+    print('job closed.');
+  }
+
+  Job call() {
+    print('begin:${DateTime.now()}');
+
+    Future.delayed(Duration(seconds: 5)).then((value) {
+      print('action:$action, name:$name');
+      print('__end:${DateTime.now()}');
+    });
+
+    return this;
+  }
+}
+
+void main() {
+  final jobName = 'jobTest';
+  final jobId = 'job1234';
+
+  final task = Job(
+    action: JobAction.run,
+    time: JobTime.every1mins,
+    name: jobName,
+    id: jobId,
+  );
+
+  final cron = Cron();
+  final schedule = Schedule.parse(task.time.expr)..name = jobId;
+
+  // ignore: implicit_call_tearoffs
+  cron.schedule(schedule, task); // append
+
+  print('startup, state:${task.action}, name:${task.name}, ${DateTime.now()}');
+  // no.1, runAt, 1mins = 60secs
+  // no.2, runAt, 2mins
+  Future.delayed(Duration(seconds: 70)).then((value) {
+    task.action = JobAction.pause;
+    task.name = jobName + task.action.name.toUpperCase();
+  });
+
+  // no.3, runAt, 3mins
+  Future.delayed(Duration(seconds: 130)).then((value) {
+    final idx = cron.indexWhere((e) => e.schedule.name == jobId);
+    print('find jobId:$jobId, index:$idx, ${DateTime.now()}');
+
+    if (idx != -1) {
+      task.action = JobAction.run;
+      task.name = jobName + task.action.name.toUpperCase();
+      task.name += '_UPDATE';
+      task.time = JobTime.every2mins;
+
+      final sched = Schedule.parse(task.time.expr);
+      // ignore: implicit_call_tearoffs
+      final st = cron.schedule(sched, task, false); // not append
+      cron.updateAt(idx, st);
+    }
+  });
+
+  // no.4, RunAt, 6mins
+  Future.delayed(Duration(minutes: 6)).then((value) {
+    final count = cron.count;
+    if (count > 0) {
+      task.action = JobAction.delete;
+      task.name = jobName + task.action.name.toUpperCase();
+      task.name += '_DELETE';
+
+      final len1 = cron.count;
+      cron.removeAt(0);
+      final len2 = cron.count;
+      print('remove index:0, length $len1 to $len2. ${DateTime.now()}');
+    }
+  });
+
+  // no.5, 10mins after close.
+  Future.delayed(Duration(minutes: 10)).then((value) {
+    print('shutdown. ${DateTime.now()}');
+    cron.close().then((value) {
+      task.cancel();
+    });
+  });
+}
diff --git a/lib/cron.dart b/lib/cron.dart
index 6ec3ac0..c19501b 100644
--- a/lib/cron.dart
+++ b/lib/cron.dart
@@ -20,11 +20,28 @@ abstract class Cron {
   /// A cron-like time-based job scheduler.
   factory Cron() => _Cron();
 
-  /// Schedules a [task] running specified by the [schedule].
-  ScheduledTask schedule(Schedule schedule, Task task);
+  /// Schedules a [task] running specified by the [schedule], if [append].
+  ScheduledTask schedule(Schedule schedule, Task task, [bool append = false]);
 
   /// Closes the cron instance and doesn't accept new tasks anymore.
   Future close();
+
+  /// Update ScheduledTask [st] at position [index] in this list _schedules.
+  void updateAt(int index, ScheduledTask st) {}
+
+  /// Remove the ScheduledTask at position [index] from list _schedules.
+  void removeAt(int index) {}
+
+  /// The first index in the list _schedules if [test] is true,
+  /// if not found returns -1.
+  /// ```dart
+  /// // search schedule name = 'sched1234' in cron instance.
+  /// final index = cron.indexWhere((e) => e.schedule.name == 'sched1234');
+  /// ```
+  int indexWhere(bool Function(ScheduledTask e) test, [int start = 0]) => -1;
+
+  /// the number of ScheduledTask in the list _schedules.
+  int get count => 0;
 }
 
 /// The cron schedule.
@@ -47,6 +64,9 @@ class Schedule {
   /// The weekdays a Task should be started.
   final List<int>? weekdays;
 
+  /// extra data, schedule name
+  late String name = '';
+
   /// Test if this schedule should run at the specified time.
   bool shouldRunAt(DateTime time) {
     if (seconds?.contains(time.second) == false) return false;
@@ -168,11 +188,27 @@ class _Cron implements Cron {
   final _schedules = <_ScheduledTask>[];
 
   @override
-  ScheduledTask schedule(Schedule schedule, Task task) {
+  int get count => _schedules.length;
+
+  @override
+  int indexWhere(bool Function(ScheduledTask) test, [int start = 0]) =>
+      _schedules.indexWhere(test, start);
+
+  @override
+  void removeAt(int index) => _schedules.removeAt(index);
+
+  @override
+  void updateAt(int i, ScheduledTask st) =>
+      _schedules[i] = st as _ScheduledTask;
+
+  @override
+  ScheduledTask schedule(Schedule schedule, Task task, [bool append = true]) {
     if (_closed) throw Exception('Closed.');
     final st = _ScheduledTask(schedule, task);
-    _schedules.add(st);
-    _scheduleNextTick();
+    if (append) {
+      _schedules.add(st);
+      _scheduleNextTick();
+    }
     return st;
   }
 
diff --git a/lib/src/constraint_parser.dart b/lib/src/constraint_parser.dart
index 10bc9df..0d675b1 100644
--- a/lib/src/constraint_parser.dart
+++ b/lib/src/constraint_parser.dart
@@ -57,5 +57,5 @@ List<int>? parseConstraint(dynamic constraint) {
 /// format and cannot be parsed or processed.
 class ScheduleParseException extends FormatException {
   /// Creates a new `FormatException` with an optional error [message].
-  ScheduleParseException([String message = '']) : super(message);
+  ScheduleParseException([super.message]);
 }
diff --git a/pubspec.yaml b/pubspec.yaml
index 76644dd..a5b99fd 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,6 +1,6 @@
 name: cron
 description: A time-based job scheduler similar to cron. Run tasks periodically at fixed times or intervals.
-version: 0.6.2
+version: 0.6.3
 repository: https://github.com/agilord/cron
 
 topics:
@@ -11,7 +11,7 @@ topics:
   - cron-time
 
 environment:
-  sdk: '>=2.12.0 <4.0.0'
+  sdk: '>=2.17.0 <4.0.0'
 
 dependencies:
   clock: ^1.1.1