https://pub.dev/documentation/syncfusion_flutter_datepicker/latest/datepicker/DateRangePickerMonthViewSettings/firstDayOfWeek.html
firstDayOfWeek property - DateRangePickerMonthViewSettings class - datepicker library - Dart API
API docs for the firstDayOfWeek property from the DateRangePickerMonthViewSettings class, for the Dart programming language.
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