why week function gives week number 0 for dates from 1.1.2024 to 7.1.2024?

[Antero]

I'm totally confused!

[yabwon]

It does not:

1    data _null_;
2    do date = '1jan2024'd to '7jan2024'd;
3      week_u=week(date, 'u');
4      week_v=week(date, 'v');
5      week_w=week(date, 'w');
6      format date yymmdd10.;
7      put (_ALL_) (=);
8    end;
9    run;

date=2024-01-01 week_u=0 week_v=1 week_w=1
date=2024-01-02 week_u=0 week_v=1 week_w=1
date=2024-01-03 week_u=0 week_v=1 week_w=1
date=2024-01-04 week_u=0 week_v=1 week_w=1
date=2024-01-05 week_u=0 week_v=1 week_w=1
date=2024-01-06 week_u=0 week_v=1 week_w=1
date=2024-01-07 week_u=1 week_v=1 week_w=1
NOTE: DATA statement used (Total process time):
      real time           0.01 seconds
      cpu time            0.01 seconds

Did you read documentation for week()? 

Bart

[PaigeMiller]

The documentation explains it clearly

The WEEK function with the U descriptor reads a SAS date value and returns the number of the week within the year. The number-of-the-week value is represented as a decimal number in the range 0–53, with a leading zero and maximum value of 53. Week 0 means that the first day of the week occurs in the preceding year. The fifth week of the year is represented as 05.

[Antero]

Google searches haven't  included those descriptors and I have missed them.

Thanks for pointing out the correct solutions!

[ballardw]

Start here : https://documentation.sas.com/?cdcId=pgmsascdc&cdcVersion=9.4_3.4&docsetId=pgmsashome&docsetTarget=h...

And search within the SAS documentation.

Depending on your install the online help could be quite extensive and no reason to "google".