Find Last 5 Weeks Number in C#

public static int GetIso8601WeekOfYear(DateTime time)

{

    DayOfWeek day = CultureInfo.InvariantCulture.Calendar.GetDayOfWeek(time);

    if (day >= DayOfWeek.Monday && day <= DayOfWeek.Wednesday)

    {

        time = time.AddDays(3);

    }

    return CultureInfo.InvariantCulture.Calendar.GetWeekOfYear(time, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);

}

 int week1 = GetIso8601WeekOfYear(DateTime.Today);

int week2 = GetIso8601WeekOfYear(DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek - 6));

int week3 = GetIso8601WeekOfYear(DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek - 12));

int week4 = GetIso8601WeekOfYear(DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek - 18));

int week5 = GetIso8601WeekOfYear(DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek - 21));