firstDayOfWeek property
DateTime
firstDayOfWeek
Implementation
DateTime get firstDayOfWeek {
/// Handle Daylight Savings by setting hour to 12:00 Noon
/// rather than the default of Midnight
final day = DateTime.utc(this.year, this.month, this.day, 12);
/// Weekday is on a 1-7 scale Monday - Sunday,
/// This Calendar works from Sunday - Monday
var decreaseNum = day.weekday % 7;
return this.subtract(Duration(days: decreaseNum));
}