// 设置每周的第一天从周日开始
extension StartOfWeek on DateTime {
  DateTime startOfWeek({int startOfWeekDay = DateTime.sunday}) {
    int diff = (7 + (weekday - startOfWeekDay)) % 7;
    DateTime dt = add(Duration(days: -diff));
    return DateTime(dt.year, dt.month, dt.day);
  }
}