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

[Denali]

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! 

[PaigeMiller]

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?

[Denali]

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

[PaigeMiller]

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;