topic Re: How to calculate difference in days between two dates (given in SAS date format)? in SAS Programming

How to calculate difference in days between two dates (given in SAS date format)?

Denali — Tue, 19 Feb 2019 20:28:05 GMT

Hi,

Each patient was asked twice to recall their date of first treatment. The dates might be inconsistent because there is recall bias. I would like to create a new variable indicating there is a huge difference between the two dates. The definition of "huge difference" could be 1 year.

Patient ID Recall date1 Recall date2 Huge Difference (This is what I want)

001 08/05/2006 09/2006 NO

002 05/24/2006 05/2007 YES

003 02/08/2007 08/2006 NO

004 08/12/2010 11/2007 YES

Given the formats were different, how do I do the calculation and create the variable I need? Thanks in advance!

Re: How to calculate difference in days between two dates (given in SAS date format)?

PaigeMiller — Tue, 19 Feb 2019 20:34:33 GMT

Are Recall_date_1 and Recall_date_2 text strings, or are they actual SAS date values? In other words, does PROC CONTENTS show these variables as numeric, or character?

Re: How to calculate difference in days between two dates (given in SAS date format)?

Denali — Tue, 19 Feb 2019 21:01:44 GMT

Both are numeric. Recall 1 has MMDDYY10. format. Recall has MMYYS7. format.

Re: How to calculate difference in days between two dates (given in SAS date format)?

PaigeMiller — Tue, 19 Feb 2019 21:14:54 GMT

So both are SAS date values, and all you need to do to determine the difference is subtract them. The formatting does not change the underlying SAS date value.

data want;
    set have;
    length huge $ 3;
    if abs(recall1-recall2)>365 then huge='YES';
    else huge='NO';
run;