firstDayWeekDayIndex property

int get firstDayWeekDayIndex

本月第一天，是周几（从周日开始算，周日为0）

Implementation

int get firstDayWeekDayIndex {
  int ret = DateTime(year, month, 1).weekday;
  if (ret == 7) {
    return 0;
  }
  return ret;
}