Enum TFirstWeekRule

The first week in the year is always the week containing the first day of the year.

If at least four days of the new year occur during the week containing the first day then this is the first week in the year. Otherwise the first week in the year is the following week. This is the default and complies with the international standard.

The first week in the year is the first week of which all seven days occur within the new year.