How can I create an event from my app? - Flutter

Like this 👇 when my users create a new online appointment inside my app I want also create an event (reminder).

@kawan-osman Based on your image I can say that you want to add your event in the iPhone Calendar app.

For that you should use package - https://pub.dev/packages/add_2_calendar in your Flutter Project and then check below sample code for event add.

Add2Calendar.addEvent2Cal( Event(
      title: 'Test eventeee',
      description: 'example',
      location: 'Flutter app',
      startDate: DateTime.now(),
      endDate: DateTime.now().add(Duration(minutes: 30)),
      allDay: false,
      iosParams: IOSParams(
        reminder: Duration(minutes: 40),
      ),
      androidParams: AndroidParams(
        emailInvites: ["test@example.com"],
      ),
    ),
);

For more detail check example of package link.