How to calculate the Week Number for a given date?

tony01 · New User Joined: 14 Sep 2005 Posts: 9

Hi everyone:

Someone can provide me a source of code to calculate the week number for a given date (Is very hard to find it .)

For example :

For Today's date November 6th, 2006,
the week number is : 45

Thanks

priyesh.agrawal · Posted: Tue Nov 07, 2006 10:16 am

sivaprasad_kode · New User Joined: 07 Nov 2006 Posts: 1 Location: Hyderabad

I dont think the below logic will work out. because When we use FUNCTION KEYWORD then we will not use COMPUTE statement as i thought. Please refer once for ensure.

priyesh.agrawal · Posted: Tue Nov 07, 2006 7:52 pm

die7nadal · Active User Joined: 23 Mar 2005 Posts: 156

If you can do it in DB2 you just need to use WEEK function and it will give you an integer 1 to 54 that represents the week of the year.

DavidatK · Posted: Wed Nov 08, 2006 3:55 am

Toney01,

When calculating the week number, what constitutes the first week. Does the first day of the first week start on January 1, or is the week defined as Monday ? Sunday, Sunday ? Saturday? If January 1 falls on a Friday, is this in the first week of this year, or the last week of last year?

Dave

tony01 · New User Joined: 14 Sep 2005 Posts: 9

Hi DavidatK:

I use Week numbers= ISO 8601 (week starts Monday), week 1 is the first week with Thursday.

For example, In year 1999, janaury 1st, falls on a friday;
and the week number for an input date = January 3th of 1999,
is week number = 53 of the last year (1998).

Look here the calendar for year 1999 and see "weekno" column:
www.timeanddate.com/calendar/custom.html?year=1999&country=27&lang=en&hol=4194329&wno=2&moon=on

So, If I use the sivaprasad_kode code to calculate week numeber for
an input date = January 3th of 1999,
I get week number = 1, which is incorrect.

So as I said before it is very tricky to find the solution.

Regards.

karnataka · New User Joined: 15 Sep 2006 Posts: 20 Location: bangalore

hi,

here i am sending source code . check it out with required date if its wrong or not meeting your requirement plz let me know

IDENTIFICATION DIVISION.
PROGRAM-ID. COMP3TST.
ENVIRONMENT DIVISION.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 WS-DATE PIC X(10) VALUE '06/11/2006'.
01 RED-DATE REDEFINES WS-DATE.
02 DD PIC 9(2).
02 FILLER PIC X.
02 MM PIC 9(2).
02 FILLER PIC X.
02 YY PIC 9(4).
01 I PIC 99 VALUE ZERO.
01 NUM-DAYS PIC 999 VALUE ZERO.
01 NUM-WEEKS PIC 999 VALUE ZERO.
01 REM-DAYS PIC 999 VALUE ZERO.
01 REM PIC 99 VALUE ZERO.
01 CHECK-LEAP PIC 99 VALUE ZERO.
01 LEAP-YEAR PIC X(3) VALUE 'NO'.
PROCEDURE DIVISION.
100-MAIN-PARA.
DIVIDE YY BY 4 GIVING REM REMAINDER CHECK-LEAP
IF CHECK-LEAP = ZERO
MOVE 'YES' TO LEAP-YEAR
END-IF.

PERFORM VARYING I FROM 1 BY 1 UNTIL I = MM
IF I = 1 OR 3 OR 5 OR 7 OR 9 OR 10 OR 12
ADD 31 TO NUM-DAYS
END-IF

IF I = 2 AND LEAP-YEAR NOT EQUAL 'YES'
ADD 28 TO NUM-DAYS
END-IF

IF I = 2 AND LEAP-YEAR = 'YES'
ADD 29 TO NUM-DAYS
END-IF

IF I = 4 OR 6 OR 8 OR 11
ADD 30 TO NUM-DAYS
END-IF
END-PERFORM.

ADD DD TO NUM-DAYS.
DIVIDE NUM-DAYS BY 7 GIVING NUM-WEEKS REMAINDER REM-DAYS.
DISPLAY "NUM-WEEKS1=>" NUM-WEEKS.
IF REM-DAYS > ZERO
ADD 1 TO NUM-WEEKS
END-IF.

DISPLAY "WS-DATE===>" WS-DATE.
DISPLAY "RED-DATE==>" RED-DATE.
DISPLAY "DD=======>" DD.
DISPLAY "MM=======>" MM.
DISPLAY "YY=======>" YY.
DISPLAY "NUM-DAYS=>" NUM-DAYS.
DISPLAY "NUM-WEEKS=>" NUM-WEEKS.
DISPLAY "REM-DAYS=>" REM-DAYS.
STOP RUN.

output:

NUM-WEEKS1=>044
WS-DATE===>06/11/2006
RED-DATE==>06/11/2006
DD=======>06
MM=======>11
YY=======>2006
NUM-DAYS=>310
NUM-WEEKS=>045
REM-DAYS=>002

week number for a date 06/11/2006 is 45

thanks

priyesh.agrawal · Posted: Wed Nov 08, 2006 10:11 am

tony01 · New User Joined: 14 Sep 2005 Posts: 9

Hi karnataka :

Your code gives me the same result as priyesh.agrawal code.

But priyesh.agrawal is funny becuase his code is not for calculating
week number . I don't know he tries to do.

I am still looking for a working code to calculate week number.

Thanks.

priyesh.agrawal · Posted: Thu Nov 09, 2006 4:01 am

tony01 · New User Joined: 14 Sep 2005 Posts: 9

Hi priyesh.agrawal :

This is much better , your code works almost perfect, but I have small problem, when I test your code with these parameters :

Input date, Jan 3th, 1999 :
MOVE 19990103 TO PA-INPUT-DATE

Todays day from day of the week: Wednesday :
MOVE 3 TO PARA-TODAYS-DAY

Current date : November 8th, 2006 :
COMPUTE PA-CURRENT-DATE = 20061108

I got week number 52 , which is incorrect, should be 53, see the calendar:
www.timeanddate.com/calendar/custom.html?year=1999&country=27&lang=en&hol=4194329&wno=2&moon=on

Can you please, fix this small problem?

Thanks so much for your help.

Regards

priyesh.agrawal · Posted: Thu Nov 09, 2006 8:13 am

Yes man... I realised that later...

If JANUARY 1ST of YEAR (INPUT-DATE) is not a MONDAY
AND
Your INPUT DATE is also in that hanging week (prior to 1st monday of the year)
This code would not work for 53rd week, but for 52nd (which is hard coded).

To include this logic also, I'll have to do the same calculation for the previous years initial dates and which causes an iteration/loop.

Anyway, some more thoughts and it should be done. for now, I m sorry, it doesnt fulfill 100%.

sreenatha · New User Joined: 21 Dec 2005 Posts: 7

tony01,

try this logic:

1) lnput date say 1999-jan-03 ( this is a sunday , hence it has to be counted as a day in 53rd week of previous year)
2) check the first day of the given year i.e 1999-jan-01 and this turns out to be friday
hence the logic will be as follws;

evaluate first-day
when 'monday'
no change in first day
when 'tuesday'
add +6 days to first-day
when 'wednesday'
add +5 days to first-day
when 'thursday'
add +4 days to first-day
when 'friday'
add +3 days to first-day
when 'saturday'
add +2 days to first-day
when 'sunday'
add+1 days to first-day
end-evaluate

hence in this case, as 1999-jan-01 was friday , the date we have to consider for calculating week is 1999-jan-04

3) now find the integer difference between the input date and first-date
i.e integer-of-date(input-date)-integer-of-date(first-date)
4) if result of step-3 is negative
week = 53
else
week=(result of step-3/7) + 1
end-if

didn't check it but hope this should work fine

DavidatK · Posted: Fri Nov 10, 2006 3:56 am

*
* THIS ROUTINE WILL CALCULATE THE WEEK NUMBER OF THE YEAR.
* THE WEEK IS DEFINED AS MOMDAY - SUNDAY. THE FIRST WEEK IS
* THE WEEK JANUARY 4 OF THE YEAR FALLS INTO. (JANUARY 1 FALLS
* ON A MONDAY - THURSDAY)
*
* IF THE INPUT DATE FALLS BEFORE THE START OF THE FIRST WEEK,
* THEN THE DATE WILL FALL INTO THE LAST WEEK OF THE PREVIOUS YEAR.
*
* IF THE INPUT DATE FALLS AFTER THE END OF THE LAST WEEK, THEN
* THE DATE WILL FALL INTO THE FIRST WEEK OF THE NEXT YEAR.
*

tony01 · New User Joined: 14 Sep 2005 Posts: 9

HI : DavidatK

I tested your code with :

Input date, Jan 3th, 1999

And I got :

week number 1 , which is incorrect, should be 53, see the calendar:
www.timeanddate.com/calendar/custom.html?year=1999&country=27?=en&hol=419

IF you can fix the code will be great!!

Thanks .

DavidatK · Posted: Fri Nov 10, 2006 9:13 pm

tony01,

I retested the code and got

.SARPAGE 4
.
.19981231 = 1998-53
.19990101 = 1998-53
.19990102 = 1998-53
.19990103 = 1998-53
.19990104 = 1999-01

I'll re-check the code I posted to see if I missed anything while cut/paste.

Dave

tony01 · New User Joined: 14 Sep 2005 Posts: 9

Yes please.

Let me know.

Thanks a lot for your efforts.

DavidatK · Posted: Sat Nov 11, 2006 2:53 am

Tony01,

I checked the code that I posted, if there is a difference, it escapes me.

This works on my processor ????????

Are you sure you ran this code?

Dave

tony01 · New User Joined: 14 Sep 2005 Posts: 9

DavidatK:

I found a small BUG in your program, and this is why
I couldn't have the correct result from my input date 19990103.

BEFORE : Condition less than
IF INTEGER-OF-INPUT-DATE < INTEGER-OF-MON-FIRSTWEEK
THEN
SUBTRACT 1 FROM WS-CURR-YYYY GIVING WS-PREV-YYYY
.
.

END-IF.

AFTER : Condition MUST BE : LESS EQUAL

IF INTEGER-OF-INPUT-DATE <= INTEGER-OF-MON-FIRSTWEEK
THEN
SUBTRACT 1 FROM WS-CURR-YYYY GIVING WS-PREV-YYYY
.
.

END-IF.

Now It works like a charm, thanks a lot for your code and for your efforts.
I appreciated very much your help.

Regards

tony01 · New User Joined: 14 Sep 2005 Posts: 9

DavidatK:

I tested year 2000 (leap year) for December 3th, 2000
I got weeknum = 49, which is wrong , should be weeknum = 48

December 30th, 2000
I got 2001-01, which is wrong , should be 2000-52

December 31st, 2000
I got 2001-01, which is wrong , should be 2000-52

In fact the code is NOT STABLE, I think is missing more logic, but should be tricki.

Anayway, still looking a TRUE solution.

Thanks

DavidatK · Posted: Tue Nov 14, 2006 5:25 am

Tony01,

I've got to stand by this code being correct. I even backloaded the code I posted and compiled that. Results of that test are:

tony01 · New User Joined: 14 Sep 2005 Posts: 9

Hi Dave:

In fact, I am working with Mainframe os/390, but the problem I think is that I don't have the FUNCTION INTGER-OF-DATE , so I am using a home routine to calculate INTEGR-OF-DATE, maybe this is the problem.
I am not sure of that.

Thanks

DavidatK · Posted: Wed Nov 15, 2006 1:30 am

Tony01,

One of the common problems with calculating the integer-of-date is that most applications are concerned with the number of days between two given dates within a normal business environment, where you are normally not concerned with dates prior to 1901 or after 2099 and are not concerned with the day of the week. The error usually comes in when calculating leap-years. Normally we consider a leap year to be a year evenly divisible by 4, and for the year between 1901 and 2099 this is true. However, if the year is evenly divisible by 100 and not evenly divisible by 400, it is NOT a leap year. Hence, 1600, 2000, 2400 are leap years, 1700, 1800, 1900, 2100 are NOT leap years. If this is not taken into account and your base year is prior to 1901, the day of the week is thrown off. Check your home code for integer-of-year to make sure it takes this into account.

Dave

dbzTHEdinosauer · Posted: Wed Nov 15, 2006 3:07 am

Dave,

excellent response, the technical was right on; i am envious of your diplomatic skills.