firstDayOfWeek property
The first day of the week, i.e. index 1 is Monday (DateTime.monday's value is 1).
Make sure to correct between ISO 8601 days and Dart const days. For more information, see the package README's "First day of week" section.
If omitted, defaultFirstDayOfWeek is used (en_ISO, Monday).
Implementation
final int firstDayOfWeek;