extension DateTimeExtension on DateTime {

  DateTime beginOfDay() {
    return DateTime(this.year, this.month, this.day);
  }

  DateTime beginOfWeek() {
    // The week is starting from Sunday
    return (this.weekday == 7) ? this : this.subtract(Duration(days: this.weekday));
  }

  DateTime endOfWeek() {
    // The last day of the week is Saturday
    return this.beginOfWeek().add(Duration(days: DateTime.daysPerWeek - 1));
  }

  DateTime beginOfMonth() {
    return DateTime(this.year, this.month);
  }

  DateTime endOfMonth() {
    return (this.month < 12) ?
      DateTime(this.year, this.month + 1, 0) :
      DateTime(this.year + 1, 1, 0);
  }
}