data property
Specifies the color and typography values for descendant calendar widgets.
Widget build(BuildContext context) {
  return Scaffold(
    body: SfCalendarTheme(
      data: SfCalendarThemeData(
        brightness: Brightness.dark,
        backgroundColor: Colors.grey
      ),
      child: SfCalendar()
    ),
  );
}
Implementation
final SfCalendarThemeData data;