给出日期，如何知道是这一年的第几周

function WeekofYear(Date: TDate): integer; 
var

FirstDay, FirstWeekEnd, NowWeekEnd: TDate;

Year, Month, Day: word;

begin

DecodeDate(Date, Year, Month, Day);

FirstDay := EncodeDate(Year, 1, 1);

FirstWeekEnd := FirstDay + 7 - DayofWeek(FirstDay);

NowWeekEnd := Date + 7 - DayofWeek(Date);

Result := Round(NowWeekEnd - FirstWeekEnd) div 7 + 1;

end;