GregorianCalendar GetWeekOfYear - bug?

[TibX]

using System.Globalization;

GregorianCalendar cal = new GregorianCalendar();

int weekNum;

weekNum = cal.GetWeekOfYear(new DateTime(2007, 12, 30),
CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);
// returns 52 (OK)

weekNum = cal.GetWeekOfYear(new DateTime(2007, 12, 31),
CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);
// returns 53 (*** correct is 1 ***)

weekNum = cal.GetWeekOfYear(new DateTime(2008, 1, 1),
CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);
// returns 1 (OK)