Crystal Report Function

Question

Post Author: y.moreau
CA Forum: Formula
I would like to convert a date as a week number. First week of the year is Week 1, week of April 12th is week 15.Thanks in advance for your help

Answer 1

Post Author: wapper
CA Forum: Formula
As a fellow european, I have to warn you: never trust american software when it comes to week numbers. In Europe, we mostly use ISO week numbering. ISO standard states that a week always starts with monday, and the first week of the year is the one that have first thursday of the year. See http://www.cpearson.com/excel/weeknum.htm
Americans use sunday as first day of the week, and I'm not quite sure whether they have a single commonly accepted rule for calculating week numbers.
The DatePart function you mentioned will calculate the week numbers incorrectly for certain dates (at least in version 8.5 I am using):
DatePart ("ww", {test_date_range.value}, crMonday, crFirstFourDays)
will display invalid values for:
date
Crystal
ISO
31.12.2001
53
1
30.12.2002
53
1
31.12.2002
53
1
29.12.2003
53
1
30.12.2003
53
1
31.12.2003
53
1
31.12.2007
53
1
29.12.2008
53
1
30.12.2008
53
1
31.12.2008
53
1
As a matter of fact, there is no week 53 in year 2007 or 2008 according to ISO standard.
As far as I know, there is no built-in function in Crystal Reports 8, or Visual Basic 6, or MSSQL, that will calculate ISO week number properly. In Crystal, I use a function like following:
//Advanced formula for calculating ISO week number and year for this week number//http://www.cpearson.com/excel/weeknum.htm
numberVar numTemp;numberVar ThisYear;dateVar PreviousYearStart;dateVar ThisYearStart;dateVar NextYearStart;
numberVar tmpWeekDay;dateVar tmpNewYear;
numberVar ISOWeekNum;numberVar YearNum;
datetimeVar datDate := {test_date_range.value};
if datDate <> Date(0,0,0)then (
    //ThisYear    ThisYear := Year(datDate);
    //ThisYearStart  - find Monday closest to Jan 1    for numTemp := -4 to 4 do    (      tmpNewYear := DateSerial(ThisYear, 1, numTemp);      if DayOfWeek(tmpNewYear,crMonday) = 1 then ThisYearStart := tmpNewYear    );        //PreviousYearStart - find Monday closest to Jan 1    for numTemp := -4 to 4 do    (      tmpNewYear := DateSerial(ThisYear-1, 1, numTemp);      if DayOfWeek(tmpNewYear,crMonday) = 1 then PreviousYearStart := tmpNewYear    );
    //NextYearStart - find Monday closest to Jan 1    for numTemp := -4 to 4 do    (      tmpNewYear := DateSerial(ThisYear+1, 1, numTemp);      if DayOfWeek(tmpNewYear,crMonday) = 1 then NextYearStart := tmpNewYear    );
    if datDate >= NextYearStart    then     (        ISOWeekNum := (datDate - NextYearStart) \ 7 + 1;        YearNum := Year(datDate) + 1    )    else        if datDate < ThisYearStart        then         (            ISOWeekNum := (datDate - PreviousYearStart) \ 7 + 1;            YearNum := Year(datDate) - 1        )        else        (               ISOWeekNum := (datDate - ThisYearStart) \ 7 + 1;            YearNum := Year(datDate)        );
ISOWeekNum)
Hope it helps.
Denis